diff --git a/esphome/components/zephyr/__init__.py b/esphome/components/zephyr/__init__.py
index b8a091feb92..348e7a3cf2d 100644
--- a/esphome/components/zephyr/__init__.py
+++ b/esphome/components/zephyr/__init__.py
@@ -122,6 +122,8 @@ def zephyr_to_code(config: ConfigType) -> None:
     zephyr_add_prj_conf("FPU", True)
     zephyr_add_prj_conf("NEWLIB_LIBC_FLOAT_PRINTF", True)
     zephyr_add_prj_conf("STD_CPP20", True)
+    # random_bytes() uses sys_rand_get() which requires the entropy subsystem
+    zephyr_add_prj_conf("ENTROPY_GENERATOR", True)
 
     # <err> os: ***** USAGE FAULT *****
     # <err> os:   Illegal load of EXC_RETURN into PC
diff --git a/esphome/core/helpers.cpp b/esphome/core/helpers.cpp
index 1f4063d7dc5..801893af183 100644
--- a/esphome/core/helpers.cpp
+++ b/esphome/core/helpers.cpp
@@ -172,6 +172,7 @@ uint32_t random_uint32() {
   // a separate bool flag (4 bytes BSS + branch on every call).
   if (splitmix32_state == 0) {
     random_bytes(reinterpret_cast<uint8_t *>(&splitmix32_state), sizeof(splitmix32_state));
+    splitmix32_state |= 1;  // ensure non-zero seed
   }
   splitmix32_state += 0x9e3779b9u;
   uint32_t z = splitmix32_state;