diff --git a/src/data/Thread.js b/src/data/Thread.js
index fdb789a..8cd79e8 100644
--- a/src/data/Thread.js
+++ b/src/data/Thread.js
@@ -223,8 +223,16 @@ class Thread {
       attachments: attachmentLinks,
     });
 
-    // Send the reply DM
     const dmContent = formatters.formatStaffReplyDM(threadMessage);
+    const inboxContent = formatters.formatStaffReplyThreadMessage(threadMessage);
+
+    // Because moderator replies have to be editable, we enforce them to fit within 1 message
+    if (! utils.messageContentIsWithinMaxLength(dmContent) || ! utils.messageContentIsWithinMaxLength(inboxContent)) {
+      await this.postSystemMessage("Reply is too long! Make sure your reply is under 2000 characters total, moderator name in the reply included.");
+      return false;
+    }
+
+    // Send the reply DM
     let dmMessage;
     try {
       dmMessage = await this._sendDMToUser(dmContent, files);
@@ -240,7 +248,6 @@ class Thread {
     });
 
     // Show the reply in the inbox thread
-    const inboxContent = formatters.formatStaffReplyThreadMessage(threadMessage);
     const inboxMessage = await this._postToThreadChannel(inboxContent, files);
     if (inboxMessage) {
       await this._updateThreadMessage(threadMessage.id, { inbox_message_id: inboxMessage.id });
@@ -719,6 +726,13 @@ class Thread {
     const formattedThreadMessage = formatters.formatStaffReplyThreadMessage(newThreadMessage);
     const formattedDM = formatters.formatStaffReplyDM(newThreadMessage);
 
+    // Same restriction as in replies. Because edits could theoretically change the number of messages a reply takes, we enforce replies
+    // to fit within 1 message to avoid the headache and issues caused by that.
+    if (! utils.messageContentIsWithinMaxLength(formattedDM) || ! utils.messageContentIsWithinMaxLength(formattedThreadMessage)) {
+      await this.postSystemMessage("Edited reply is too long! Make sure the edit is under 2000 characters total, moderator name in the reply included.");
+      return false;
+    }
+
     await bot.editMessage(threadMessage.dm_channel_id, threadMessage.dm_message_id, formattedDM);
     await bot.editMessage(this.channel_id, threadMessage.inbox_message_id, formattedThreadMessage);
 
diff --git a/src/utils.js b/src/utils.js
index d97447a..83118fe 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -336,6 +336,56 @@ function readMultilineConfigValue(str) {
 
 function noop() {}
 
+// https://discord.com/developers/docs/resources/channel#create-message-params
+const MAX_MESSAGE_CONTENT_LENGTH = 2000;
+
+// https://discord.com/developers/docs/resources/channel#embed-limits
+const MAX_EMBED_CONTENT_LENGTH = 6000;
+
+/**
+ * Checks if the given message content is within Discord's message length limits.
+ *
+ * Based on testing, Discord appears to enforce length limits (at least in the client)
+ * the same way JavaScript does, using the UTF-16 byte count as the number of characters.
+ *
+ * @param {string|Eris.MessageContent} content
+ */
+function messageContentIsWithinMaxLength(content) {
+  if (typeof content === "string") {
+    content = { content };
+  }
+
+  if (content.content && content.content.length > MAX_MESSAGE_CONTENT_LENGTH) {
+    return false;
+  }
+
+  if (content.embed) {
+    let embedContentLength = 0;
+
+    if (content.embed.title) embedContentLength += content.embed.title.length;
+    if (content.embed.description) embedContentLength += content.embed.description.length;
+    if (content.embed.footer && content.embed.footer.text) {
+      embedContentLength += content.embed.footer.text.length;
+    }
+    if (content.embed.author && content.embed.author.name) {
+      embedContentLength += content.embed.author.name.length;
+    }
+
+    if (content.embed.fields) {
+      for (const field of content.embed.fields) {
+        if (field.title) embedContentLength += field.name.length;
+        if (field.description) embedContentLength += field.value.length;
+      }
+    }
+
+    if (embedContentLength > MAX_EMBED_CONTENT_LENGTH) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
 module.exports = {
   BotError,
 
@@ -377,5 +427,7 @@ module.exports = {
 
   readMultilineConfigValue,
 
+  messageContentIsWithinMaxLength,
+
   noop,
 };