diff --git a/esphome/core/helpers.cpp b/esphome/core/helpers.cpp
index 09e755ca71..9f850b5df8 100644
--- a/esphome/core/helpers.cpp
+++ b/esphome/core/helpers.cpp
@@ -545,38 +545,36 @@ static inline bool is_base64(char c) { return (isalnum(c) || (c == '+') || (c ==
 
 std::string base64_encode(const std::vector<uint8_t> &buf) { return base64_encode(buf.data(), buf.size()); }
 
+// Encode 3 input bytes to 4 base64 characters, append 'count' to ret.
+static inline void base64_encode_triple(const char *char_array_3, int count, std::string &ret) {
+  char char_array_4[4];
+  char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
+  char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
+  char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
+  char_array_4[3] = char_array_3[2] & 0x3f;
+
+  for (int j = 0; j < count; j++)
+    ret += BASE64_CHARS[static_cast<uint8_t>(char_array_4[j])];
+}
+
 std::string base64_encode(const uint8_t *buf, size_t buf_len) {
   std::string ret;
   int i = 0;
-  int j = 0;
   char char_array_3[3];
-  char char_array_4[4];
 
   while (buf_len--) {
     char_array_3[i++] = *(buf++);
     if (i == 3) {
-      char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
-      char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
-      char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
-      char_array_4[3] = char_array_3[2] & 0x3f;
-
-      for (i = 0; (i < 4); i++)
-        ret += BASE64_CHARS[static_cast<uint8_t>(char_array_4[i])];
+      base64_encode_triple(char_array_3, 4, ret);
       i = 0;
     }
   }
 
   if (i) {
-    for (j = i; j < 3; j++)
+    for (int j = i; j < 3; j++)
       char_array_3[j] = '\0';
 
-    char_array_4[0] = (char_array_3[0] & 0xfc) >> 2;
-    char_array_4[1] = ((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4);
-    char_array_4[2] = ((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6);
-    char_array_4[3] = char_array_3[2] & 0x3f;
-
-    for (j = 0; (j < i + 1); j++)
-      ret += BASE64_CHARS[static_cast<uint8_t>(char_array_4[j])];
+    base64_encode_triple(char_array_3, i + 1, ret);
 
     while ((i++ < 3))
       ret += '=';
@@ -589,13 +587,33 @@ size_t base64_decode(const std::string &encoded_string, uint8_t *buf, size_t buf
   return base64_decode(reinterpret_cast<const uint8_t *>(encoded_string.data()), encoded_string.size(), buf, buf_len);
 }
 
+// Decode 4 base64 characters to up to 'count' output bytes, returns true if truncated.
+static inline bool base64_decode_quad(uint8_t *char_array_4, int count, uint8_t *buf, size_t buf_len, size_t &out) {
+  for (int i = 0; i < 4; i++)
+    char_array_4[i] = base64_find_char(char_array_4[i]);
+
+  uint8_t char_array_3[3];
+  char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
+  char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
+  char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
+
+  bool truncated = false;
+  for (int j = 0; j < count; j++) {
+    if (out < buf_len) {
+      buf[out++] = char_array_3[j];
+    } else {
+      truncated = true;
+    }
+  }
+  return truncated;
+}
+
 size_t base64_decode(const uint8_t *encoded_data, size_t encoded_len, uint8_t *buf, size_t buf_len) {
   size_t in_len = encoded_len;
   int i = 0;
-  int j = 0;
   size_t in = 0;
   size_t out = 0;
-  uint8_t char_array_4[4], char_array_3[3];
+  uint8_t char_array_4[4];
   bool truncated = false;
 
   // SAFETY: The loop condition checks is_base64() before processing each character.
@@ -605,42 +623,16 @@ size_t base64_decode(const uint8_t *encoded_data, size_t encoded_len, uint8_t *b
     char_array_4[i++] = encoded_data[in];
     in++;
     if (i == 4) {
-      for (i = 0; i < 4; i++)
-        char_array_4[i] = base64_find_char(char_array_4[i]);
-
-      char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
-      char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
-      char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
-
-      for (i = 0; i < 3; i++) {
-        if (out < buf_len) {
-          buf[out++] = char_array_3[i];
-        } else {
-          truncated = true;
-        }
-      }
+      truncated |= base64_decode_quad(char_array_4, 3, buf, buf_len, out);
       i = 0;
     }
   }
 
   if (i) {
-    for (j = i; j < 4; j++)
+    for (int j = i; j < 4; j++)
       char_array_4[j] = 0;
 
-    for (j = 0; j < 4; j++)
-      char_array_4[j] = base64_find_char(char_array_4[j]);
-
-    char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
-    char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
-    char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
-
-    for (j = 0; j < i - 1; j++) {
-      if (out < buf_len) {
-        buf[out++] = char_array_3[j];
-      } else {
-        truncated = true;
-      }
-    }
+    truncated |= base64_decode_quad(char_array_4, i - 1, buf, buf_len, out);
   }
 
   if (truncated) {