diff --git a/src/gn/rust_project_writer.cc b/src/gn/rust_project_writer.cc
index 4e66dcc..eea527c 100644
--- a/src/gn/rust_project_writer.cc
+++ b/src/gn/rust_project_writer.cc
@@ -10,6 +10,7 @@
 #include <tuple>
 
 #include "base/json/string_escape.h"
+#include "base/strings/string_split.h"
 #include "gn/builder.h"
 #include "gn/deps_iterator.h"
 #include "gn/ninja_target_command_util.h"
@@ -329,6 +330,17 @@
     }
   }
 
+  // Note any environment variables. These may be used by proc macros
+  // invoked by the current crate (so we want to record these for all crates,
+  // not just proc macro crates)
+  for (const auto& env_var : target->config_values().rustenv()) {
+    std::vector<std::string> parts = base::SplitString(
+        env_var, "=", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
+    if (parts.size() >= 2) {
+      crate.AddRustenv(parts[0], parts[1]);
+    }
+  }
+
   // Add the rest of the crate dependencies.
   for (const auto& dep : crate_deps) {
     auto idx = lookup[dep];
@@ -436,8 +448,29 @@
       rust_project << "        \"" << escaped_config << "\"";
     }
     rust_project << NEWLINE;
-    rust_project << "      ]" NEWLINE;  // end cfgs
+    rust_project << "      ]";  // end cfgs
 
+    if (!crate.rustenv().empty()) {
+      rust_project << "," NEWLINE;
+      rust_project << "      \"env\": {";
+      bool first_env = true;
+      for (const auto& env : crate.rustenv()) {
+        if (!first_env)
+          rust_project << ",";
+        first_env = false;
+        std::string escaped_key, escaped_val;
+        base::EscapeJSONString(env.first, false, &escaped_key);
+        base::EscapeJSONString(env.second, false, &escaped_val);
+        rust_project << NEWLINE;
+        rust_project << "        \"" << escaped_key << "\": \"" << escaped_val
+                     << "\"";
+      }
+
+      rust_project << NEWLINE;
+      rust_project << "      }" NEWLINE;  // end env vars
+    } else {
+      rust_project << NEWLINE;
+    }
     rust_project << "    }";  // end crate
   }
   rust_project << NEWLINE "  ]" NEWLINE;  // end crate list
diff --git a/src/gn/rust_project_writer_helpers.h b/src/gn/rust_project_writer_helpers.h
index d53ff07..24b13d0 100644
--- a/src/gn/rust_project_writer_helpers.h
+++ b/src/gn/rust_project_writer_helpers.h
@@ -14,6 +14,7 @@
 #include <unordered_map>
 #include <vector>
 
+#include "base/containers/flat_map.h"
 #include "build_settings.h"
 #include "gn/source_file.h"
 #include "gn/target.h"
@@ -44,6 +45,11 @@
   // Add a config item to the crate.
   void AddConfigItem(std::string cfg_item) { configs_.push_back(cfg_item); }
 
+  // Add a key-value environment variable pair used when building this crate.
+  void AddRustenv(std::string key, std::string value) {
+    rustenv_.emplace(key, value);
+  }
+
   // Add another crate as a dependency of this one.
   void AddDependency(CrateIndex index, std::string name) {
     deps_.push_back(std::make_pair(index, name));
@@ -91,6 +97,10 @@
     return proc_macro_dynamic_library_;
   }
 
+  // Returns environment variables applied to this, which may be necessary
+  // for correct functioning of environment variables
+  const base::flat_map<std::string, std::string>& rustenv() { return rustenv_; }
+
  private:
   SourceFile root_;
   CrateIndex index_;
@@ -101,6 +111,7 @@
   std::optional<std::string> compiler_target_;
   std::vector<std::string> compiler_args_;
   std::optional<OutputFile> proc_macro_dynamic_library_;
+  base::flat_map<std::string, std::string> rustenv_;
 };
 
 using CrateList = std::vector<Crate>;
diff --git a/src/gn/rust_project_writer_unittest.cc b/src/gn/rust_project_writer_unittest.cc
index 77a9d34..2d4f0dc 100644
--- a/src/gn/rust_project_writer_unittest.cc
+++ b/src/gn/rust_project_writer_unittest.cc
@@ -535,6 +535,8 @@
   target.sources().push_back(lib);
   target.source_types_used().Set(SourceFile::SOURCE_RS);
   target.rust_values().set_crate_root(lib);
+  target.config_values().rustenv().push_back("TEST_ENV_VAR=baz");
+  target.config_values().rustenv().push_back("TEST_ENV_VAR2=baz2");
   target.rust_values().crate_name() = "foo";
   target.config_values().rustflags().push_back("--cfg=feature=\"foo_enabled\"");
   target.SetToolchain(setup.toolchain());
@@ -568,7 +570,11 @@
       "        \"test\",\n"
       "        \"debug_assertions\",\n"
       "        \"feature=\\\"foo_enabled\\\"\"\n"
-      "      ]\n"
+      "      ],\n"
+      "      \"env\": {\n"
+      "        \"TEST_ENV_VAR\": \"baz\",\n"
+      "        \"TEST_ENV_VAR2\": \"baz2\"\n"
+      "      }\n"
       "    }\n"
       "  ]\n"
       "}\n";