diff --git a/amaranth/sim/pysim.py b/amaranth/sim/pysim.py
index 866e51b..cf98935 100644
--- a/amaranth/sim/pysim.py
+++ b/amaranth/sim/pysim.py
@@ -1,8 +1,6 @@
 from contextlib import contextmanager
 import itertools
 import re
-from vcd import VCDWriter
-from vcd.gtkw import GTKWSave
 
 from ..hdl import *
 from ..hdl._repr import *
@@ -39,6 +37,10 @@ class _VCDWriter:
             raise NotImplementedError
 
     def __init__(self, fragment, *, vcd_file, gtkw_file=None, traces=()):
+        # Although pyvcd is a mandatory dependency, be resilient and import it as needed, so that
+        # the simulator is still usable if it's not installed for some reason.
+        import vcd, vcd.gtkw
+
         if isinstance(vcd_file, str):
             vcd_file = open(vcd_file, "w")
         if isinstance(gtkw_file, str):
@@ -47,13 +49,13 @@ class _VCDWriter:
         self.vcd_signal_vars = SignalDict()
         self.vcd_memory_vars = {}
         self.vcd_file = vcd_file
-        self.vcd_writer = vcd_file and VCDWriter(self.vcd_file,
+        self.vcd_writer = vcd_file and vcd.VCDWriter(self.vcd_file,
             timescale="1 ps", comment="Generated by Amaranth")
 
         self.gtkw_signal_names = SignalDict()
         self.gtkw_memory_names = {}
         self.gtkw_file = gtkw_file
-        self.gtkw_save = gtkw_file and GTKWSave(self.gtkw_file)
+        self.gtkw_save = gtkw_file and vcd.gtkw.GTKWSave(self.gtkw_file)
 
         self.traces = []