diff --git a/fd_helper_other_test.go b/fd_helper_other_test.go
new file mode 100644
index 0000000..9cb5152
--- /dev/null
+++ b/fd_helper_other_test.go
@@ -0,0 +1,14 @@
+//go:build !zos
+// +build !zos
+
+package pty
+
+import (
+	"os"
+	"testing"
+)
+
+func getNonBlockingFile(t *testing.T, file *os.File, path string) *os.File {
+	t.Helper()
+	return file
+}
diff --git a/fd_helper_zos_test.go b/fd_helper_zos_test.go
new file mode 100644
index 0000000..ffb0373
--- /dev/null
+++ b/fd_helper_zos_test.go
@@ -0,0 +1,20 @@
+//go:build zos
+// +build zos
+
+package pty
+
+import (
+	"os"
+	"testing"
+)
+
+func getNonBlockingFile(t *testing.T, file *os.File, path string) *os.File {
+	t.Helper()
+	// z/OS doesn't open a pollable FD - fix that here
+	if _, err := fcntl(uintptr(file.Fd()), F_SETFL, O_NONBLOCK); err != nil {
+		t.Fatalf("Error: zos-nonblock: %s.\n", err)
+	}
+	nf := os.NewFile(file.Fd(), path)
+	t.Cleanup(func() { _ = nf.Close() })
+	return nf
+}
diff --git a/io_test.go b/io_test.go
index 2d88a50..922f9c1 100644
--- a/io_test.go
+++ b/io_test.go
@@ -106,9 +106,12 @@ func prepare(t *testing.T) (ptmx *os.File, done func()) {
 	if err != nil {
 		t.Fatalf("Error: open: %s.\n", err)
 	}
-	t.Cleanup(func() { _ = ptmx.Close() })
+	_ptmx := ptmx
+	t.Cleanup(func() { _ = _ptmx.Close() })
 	t.Cleanup(func() { _ = pts.Close() })
 
+	ptmx = getNonBlockingFile(t, ptmx, "/dev/ptmx")
+
 	ctx, done := context.WithCancel(context.Background())
 	t.Cleanup(done)
 	go func() {
diff --git a/pty_unsupported.go b/pty_unsupported.go
index c771020..0971dc7 100644
--- a/pty_unsupported.go
+++ b/pty_unsupported.go
@@ -1,5 +1,5 @@
-//go:build !linux && !darwin && !freebsd && !dragonfly && !netbsd && !openbsd && !solaris
-// +build !linux,!darwin,!freebsd,!dragonfly,!netbsd,!openbsd,!solaris
+//go:build !linux && !darwin && !freebsd && !dragonfly && !netbsd && !openbsd && !solaris && !zos
+// +build !linux,!darwin,!freebsd,!dragonfly,!netbsd,!openbsd,!solaris,!zos
 
 package pty
 
diff --git a/pty_zos.go b/pty_zos.go
new file mode 100644
index 0000000..18e61e1
--- /dev/null
+++ b/pty_zos.go
@@ -0,0 +1,141 @@
+//go:build zos
+// +build zos
+
+package pty
+
+import (
+	"os"
+	"runtime"
+	"syscall"
+	"unsafe"
+)
+
+const (
+	SYS_UNLOCKPT     = 0x37B
+	SYS_GRANTPT      = 0x37A
+	SYS_POSIX_OPENPT = 0xC66
+	SYS_FCNTL        = 0x18C
+	SYS___PTSNAME_A  = 0x718
+
+	SETCVTON = 1
+
+	O_NONBLOCK = 0x04
+
+	F_SETFL       = 4
+	F_CONTROL_CVT = 13
+)
+
+type f_cnvrt struct {
+	Cvtcmd int32
+	Pccsid int16
+	Fccsid int16
+}
+
+func open() (pty, tty *os.File, err error) {
+	ptmxfd, err := openpt(os.O_RDWR | syscall.O_NOCTTY)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	// Needed for z/OS so that the characters are not garbled if ptyp* is untagged
+	cvtreq := f_cnvrt{Cvtcmd: SETCVTON, Pccsid: 0, Fccsid: 1047}
+	if _, err = fcntl(uintptr(ptmxfd), F_CONTROL_CVT, uintptr(unsafe.Pointer(&cvtreq))); err != nil {
+		return nil, nil, err
+	}
+
+	p := os.NewFile(uintptr(ptmxfd), "/dev/ptmx")
+	if p == nil {
+		return nil, nil, err
+	}
+
+	// In case of error after this point, make sure we close the ptmx fd.
+	defer func() {
+		if err != nil {
+			_ = p.Close() // Best effort.
+		}
+	}()
+
+	sname, err := ptsname(ptmxfd)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	_, err = grantpt(ptmxfd)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if _, err = unlockpt(ptmxfd); err != nil {
+		return nil, nil, err
+	}
+
+	ptsfd, err := syscall.Open(sname, os.O_RDWR|syscall.O_NOCTTY, 0)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	if _, err = fcntl(uintptr(ptsfd), F_CONTROL_CVT, uintptr(unsafe.Pointer(&cvtreq))); err != nil {
+		return nil, nil, err
+	}
+
+	t := os.NewFile(uintptr(ptsfd), sname)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return p, t, nil
+}
+
+func openpt(oflag int) (fd int, err error) {
+	r0, _, e1 := runtime.CallLeFuncWithErr(runtime.GetZosLibVec()+SYS_POSIX_OPENPT<<4, uintptr(oflag))
+	fd = int(r0)
+	if e1 != 0 {
+		err = syscall.Errno(e1)
+	}
+	return
+}
+
+func fcntl(fd uintptr, cmd int, arg uintptr) (val int, err error) {
+	r0, _, e1 := runtime.CallLeFuncWithErr(runtime.GetZosLibVec()+SYS_FCNTL<<4, uintptr(fd), uintptr(cmd), arg)
+	val = int(r0)
+	if e1 != 0 {
+		err = syscall.Errno(e1)
+	}
+	return
+}
+
+func ptsname(fd int) (name string, err error) {
+	r0, _, e1 := runtime.CallLeFuncWithPtrReturn(runtime.GetZosLibVec()+SYS___PTSNAME_A<<4, uintptr(fd))
+	name = u2s(unsafe.Pointer(r0))
+	if e1 != 0 {
+		err = syscall.Errno(e1)
+	}
+	return
+}
+
+func grantpt(fildes int) (rc int, err error) {
+	r0, _, e1 := runtime.CallLeFuncWithErr(runtime.GetZosLibVec()+SYS_GRANTPT<<4, uintptr(fildes))
+	rc = int(r0)
+	if e1 != 0 {
+		err = syscall.Errno(e1)
+	}
+	return
+}
+
+func unlockpt(fildes int) (rc int, err error) {
+	r0, _, e1 := runtime.CallLeFuncWithErr(runtime.GetZosLibVec()+SYS_UNLOCKPT<<4, uintptr(fildes))
+	rc = int(r0)
+	if e1 != 0 {
+		err = syscall.Errno(e1)
+	}
+	return
+}
+
+func u2s(cstr unsafe.Pointer) string {
+	str := (*[1024]uint8)(cstr)
+	i := 0
+	for str[i] != 0 {
+		i++
+	}
+	return string(str[:i])
+}