diff --git a/lib/Test/MockFile.pm b/lib/Test/MockFile.pm
index e4a9f75..fb58f67 100644
--- a/lib/Test/MockFile.pm
+++ b/lib/Test/MockFile.pm
@@ -1853,6 +1853,7 @@ sub __open (*;$@) {
     my $rw = '';
     $rw .= 'r' if grep { $_ eq $mode } qw/+< +> +>> </;
     $rw .= 'w' if grep { $_ eq $mode } qw/+< +> +>> > >>/;
+    $rw .= 'a' if grep { $_ eq $mode } qw/>> +>>/;
 
     my $filefh = IO::File->new;
     tie *{$filefh}, 'Test::MockFile::FileHandle', $abs_path, $rw;
@@ -1943,6 +1944,8 @@ sub __sysopen (*$$;$) {
       : $rd_wr_mode == O_RDWR   ? 'rw'
       :                           confess("Unexpected sysopen read/write mode ($rd_wr_mode)");    # O_WRONLY| O_RDWR mode makes no sense and we should die.
 
+    $rw .= 'a' if $sysopen_mode & O_APPEND;
+
     # If contents is undef, we act like the file isn't there.
     if ( !defined $mock_file->{'contents'} && $rd_wr_mode == O_RDONLY ) {
         $! = ENOENT;
diff --git a/lib/Test/MockFile/FileHandle.pm b/lib/Test/MockFile/FileHandle.pm
index b8a6692..82e8355 100644
--- a/lib/Test/MockFile/FileHandle.pm
+++ b/lib/Test/MockFile/FileHandle.pm
@@ -69,11 +69,12 @@ sub TIEHANDLE {
     length $file or die("No file name passed!");
 
     my $self = bless {
-        'file'  => $file,
-        'data'  => $files_being_mocked->{$file},
-        'tell'  => 0,
-        'read'  => $mode =~ m/r/ ? 1 : 0,
-        'write' => $mode =~ m/w/ ? 1 : 0,
+        'file'   => $file,
+        'data'   => $files_being_mocked->{$file},
+        'tell'   => 0,
+        'read'   => $mode =~ m/r/ ? 1 : 0,
+        'write'  => $mode =~ m/w/ ? 1 : 0,
+        'append' => $mode =~ m/a/ ? 1 : 0,
     }, $class;
 
     # This ref count can't hold the object from getting released.
@@ -88,10 +89,13 @@ This method will be triggered every time the tied handle is printed to
 with the print() or say() functions. Beyond its self reference it also
 expects the list that was passed to the print function.
 
-We append to
-C<$Test::MockFile::files_being_mocked{$file}->{'contents'}> with what
-was sent. If the file handle wasn't opened in a read mode, then this
-call with throw EBADF via $!
+In append mode (C<< >> >> or C<< +>> >>), output is always written at
+the end of the file contents. In other write modes, output is written
+at the current tell position, overwriting existing bytes. The tell
+position advances by the number of bytes written.
+
+If the file handle wasn't opened in a write mode, this call will set
+C<$!> to EBADF and return.
 
 =cut
 
@@ -107,13 +111,38 @@ sub PRINT {
         return;
     }
 
-    my $starting_bytes = length $self->{'data'}->{'contents'};
-    foreach my $line (@list) {
-        next if !defined $line;
-        $self->{'data'}->{'contents'} .= $line;
+    # Build the output string: join with $, (output field separator) if set.
+    my $output = '';
+    for my $i ( 0 .. $#list ) {
+        $output .= $list[$i] if defined $list[$i];
+        $output .= $, if defined $, && $i < $#list;
+    }
+
+    # Append output record separator ($\) when set explicitly by the caller.
+    # Note: say() does NOT set $\ for tied handles (Perl handles its newline
+    # at the C level after PRINT returns), so this only covers explicit usage.
+    $output .= $\ if defined $\;
+
+    my $tell     = $self->{'tell'};
+    my $contents = \$self->{'data'}->{'contents'};
+
+    if ( $self->{'append'} ) {
+        # Append mode (>> / +>>): always write at end regardless of tell.
+        $$contents .= $output;
+        $self->{'tell'} = length $$contents;
+    }
+    else {
+        # Overwrite at tell position (>, +<, +>).
+        # Pad with null bytes if tell is past end of current contents.
+        my $content_len = length $$contents;
+        if ( $tell > $content_len ) {
+            $$contents .= "\0" x ( $tell - $content_len );
+        }
+        substr( $$contents, $tell, length($output), $output );
+        $self->{'tell'} = $tell + length($output);
     }
 
-    return length( $self->{'data'}->{'contents'} ) - $starting_bytes;
+    return length($output);
 }
 
 =head2 PRINTF
diff --git a/t/write_tell.t b/t/write_tell.t
new file mode 100644
index 0000000..eb850e6
--- /dev/null
+++ b/t/write_tell.t
@@ -0,0 +1,245 @@
+#!/usr/bin/perl -w
+
+use strict;
+use warnings;
+
+use Test2::Bundle::Extended;
+use Test2::Tools::Explain;
+use Test2::Plugin::NoWarnings;
+
+use Fcntl qw( O_RDWR O_CREAT O_TRUNC O_WRONLY );
+
+use Test::MockFile qw< nostrict >;
+
+{
+    note "--- tell() advances after print ---";
+
+    my $mock = Test::MockFile->file('/fake/write_tell');
+    open( my $fh, '>', '/fake/write_tell' ) or die;
+
+    is( tell($fh), 0, "tell is 0 before any writes" );
+
+    print $fh "Hello";
+    is( tell($fh), 5, "tell is 5 after printing 'Hello'" );
+
+    print $fh " World";
+    is( tell($fh), 11, "tell is 11 after printing ' World'" );
+
+    close $fh;
+    is( $mock->contents, "Hello World", "Contents are correct" );
+}
+
+{
+    note "--- tell() advances after printf ---";
+
+    my $mock = Test::MockFile->file('/fake/printf_tell');
+    open( my $fh, '>', '/fake/printf_tell' ) or die;
+
+    printf $fh "%04d", 42;
+    is( tell($fh), 4, "tell is 4 after printf '%04d'" );
+
+    printf $fh "-%s-", "test";
+    is( tell($fh), 10, "tell is 10 after second printf" );
+
+    close $fh;
+    is( $mock->contents, "0042-test-", "Contents are correct" );
+}
+
+{
+    note "--- tell() advances after syswrite ---";
+
+    my $mock = Test::MockFile->file('/fake/syswrite_tell');
+    sysopen( my $fh, '/fake/syswrite_tell', O_WRONLY | O_CREAT | O_TRUNC ) or die;
+
+    syswrite( $fh, "ABCDE", 5 );
+    is( tell($fh), 5, "tell is 5 after syswrite of 5 bytes" );
+
+    syswrite( $fh, "FGH", 3 );
+    is( tell($fh), 8, "tell is 8 after syswrite of 3 more bytes" );
+
+    close $fh;
+    is( $mock->contents, "ABCDEFGH", "Contents are correct" );
+}
+
+{
+    note "--- tell() after write then read (read+write mode) ---";
+
+    my $mock = Test::MockFile->file('/fake/rw_tell');
+    sysopen( my $fh, '/fake/rw_tell', O_RDWR | O_CREAT | O_TRUNC ) or die;
+
+    syswrite( $fh, "Hello World", 11 );
+    is( tell($fh), 11, "tell is 11 after writing 'Hello World'" );
+
+    seek( $fh, 0, 0 );
+    is( tell($fh), 0, "tell is 0 after seeking to start" );
+
+    my $buf = "";
+    read( $fh, $buf, 5 );
+    is( $buf,      "Hello", "Read back 'Hello'" );
+    is( tell($fh), 5,       "tell is 5 after reading 5 bytes" );
+}
+
+{
+    note "--- tell() after append mode ---";
+
+    my $mock = Test::MockFile->file( '/fake/append_tell', "existing" );
+    open( my $fh, '>>', '/fake/append_tell' ) or die;
+
+    print $fh " data";
+    is( tell($fh), 13, "tell is 13 after appending to 'existing'" );
+
+    close $fh;
+    is( $mock->contents, "existing data", "Contents are correct" );
+}
+
+{
+    note "--- printing undef does not change tell ---";
+
+    my $mock = Test::MockFile->file('/fake/undef_tell');
+    open( my $fh, '>', '/fake/undef_tell' ) or die;
+
+    print $fh "ABC";
+    is( tell($fh), 3, "tell is 3 after printing 'ABC'" );
+
+    print $fh undef;
+    is( tell($fh), 3, "tell unchanged after printing undef" );
+
+    close $fh;
+    is( $mock->contents, "ABC", "Contents are correct" );
+}
+
+{
+    note "--- print with explicit output record separator ---";
+
+    my $mock = Test::MockFile->file('/fake/ors_tell');
+    open( my $fh, '>', '/fake/ors_tell' ) or die;
+
+    {
+        local $\ = "\n";
+        print $fh "Hello";
+    }
+    is( tell($fh), 6, "tell is 6 after print with ORS (5 chars + newline)" );
+
+    close $fh;
+    is( $mock->contents, "Hello\n", "Contents include newline from output record separator" );
+}
+
+# Note: say() with tied filehandles does NOT append the newline via $\.
+# Perl handles say's newline at the C level (pp_print) after the tied
+# PRINT method returns, so it is never passed to PRINT. This is a known
+# limitation of tied filehandles in Perl.
+
+{
+    note "--- +< mode: seek + print overwrites at tell position ---";
+
+    my $mock = Test::MockFile->file( '/fake/rw_overwrite', "Hello World!" );
+    open( my $fh, '+<', '/fake/rw_overwrite' ) or die;
+
+    # Seek to position 6 and overwrite
+    seek( $fh, 6, 0 );
+    is( tell($fh), 6, "tell is 6 after seek" );
+
+    print $fh "Perl!";
+    is( tell($fh), 11, "tell is 11 after printing 5 bytes at position 6" );
+
+    close $fh;
+    is( $mock->contents, "Hello Perl!!", "Overwrite at position 6 replaces 'World' with 'Perl!'" );
+}
+
+{
+    note "--- +< mode: seek + print does not extend past original when write fits ---";
+
+    my $mock = Test::MockFile->file( '/fake/rw_exact', "ABCDEFGH" );
+    open( my $fh, '+<', '/fake/rw_exact' ) or die;
+
+    seek( $fh, 3, 0 );
+    print $fh "XY";
+
+    close $fh;
+    is( $mock->contents, "ABCXYFGH", "Overwrite at position 3 replaces 2 bytes" );
+}
+
+{
+    note "--- +< mode: print at tell 0 overwrites from start ---";
+
+    my $mock = Test::MockFile->file( '/fake/rw_start', "old content" );
+    open( my $fh, '+<', '/fake/rw_start' ) or die;
+
+    # tell starts at 0
+    print $fh "NEW";
+
+    close $fh;
+    is( $mock->contents, "NEW content", "Print at position 0 overwrites first 3 bytes" );
+}
+
+{
+    note "--- +< mode: print extending past end grows the file ---";
+
+    my $mock = Test::MockFile->file( '/fake/rw_extend', "short" );
+    open( my $fh, '+<', '/fake/rw_extend' ) or die;
+
+    seek( $fh, 3, 0 );
+    print $fh "LONGER";
+
+    close $fh;
+    is( $mock->contents, "shoLONGER", "Print past end extends the file" );
+    is( length( $mock->contents ), 9, "File length is 9" );
+}
+
+{
+    note "--- >> mode: seek then print still appends ---";
+
+    my $mock = Test::MockFile->file( '/fake/append_seek', "AAAA" );
+    open( my $fh, '>>', '/fake/append_seek' ) or die;
+
+    # Even after seeking to 0, append mode writes at end
+    seek( $fh, 0, 0 );
+    print $fh "BB";
+
+    close $fh;
+    is( $mock->contents, "AAAABB", "Append mode ignores seek position" );
+}
+
+{
+    note "--- +< mode: interleaved read and write ---";
+
+    my $mock = Test::MockFile->file( '/fake/rw_interleave', "Hello World" );
+    open( my $fh, '+<', '/fake/rw_interleave' ) or die;
+
+    # Read first 5 bytes
+    my $buf;
+    read( $fh, $buf, 5 );
+    is( $buf,      "Hello", "Read 'Hello'" );
+    is( tell($fh), 5,       "tell is 5 after read" );
+
+    # Write at current position (overwrite ' World' with ' Perl!')
+    print $fh " Perl!";
+    is( tell($fh), 11, "tell is 11 after write" );
+
+    close $fh;
+    is( $mock->contents, "Hello Perl!", "Interleaved read+write produces correct output" );
+}
+
+{
+    note "--- > mode: print writes at tell position (not append) ---";
+
+    my $mock = Test::MockFile->file('/fake/write_overwrite');
+    open( my $fh, '>', '/fake/write_overwrite' ) or die;
+
+    # Write initial content
+    print $fh "ABCDEFGH";
+    is( tell($fh), 8, "tell is 8 after initial write" );
+
+    # Seek back and overwrite
+    seek( $fh, 2, 0 );
+    print $fh "XY";
+    is( tell($fh), 4, "tell is 4 after overwrite" );
+
+    close $fh;
+    is( $mock->contents, "ABXYEFGH", "Overwrite in > mode at seek position" );
+}
+
+is( \%Test::MockFile::files_being_mocked, {}, "No mock files are in cache" );
+
+done_testing();
+exit;