How to Transfer Tumblr Posts to Another Accountby Melly Parker
Tumblr offers no functionality to transfer all blog posts from one Tumblr account to another, though you can share secondary blogs or move them between accounts. The name and URL of your blog can be changed, but the change doesn't remove followers or comments you've made on other users' content. Transfer your Tumblr posts manually or with a service designed to assist you if you want to move old Tumblr content to a new account.
Secondary Tumblr Accounts
Secondary Tumblr blogs can be shared between accounts, which means both accounts have access to all the posts made on that blog. To add a new Tumblr account as a user, sign in to your old account, click on the name of the secondary blog and then click "Members." Assign your new blog as a member; you have to sign back in to the new Tumblr blog to accept the invitation. Once the account is active as a blog member, use the old Tumblr account to enter the "Members" area again and promote the new account to admin. Once the new Tumblr account has full access, you can remove the old Tumblr account from the blog, if you choose.
If you navigate to the beginning of your old Tumblr blog, you can reblog posts in the order that you originally uploaded them. The new posts will not appear to be originally uploaded by your new account, though, and will show the likes and comments that people have left on the content since it was posted. You have the option to leave a new comment on any posts you reblog; if you want to lead old followers to your new blog, posting a comment like "Copying this from my old Tumblr account" may help them find your new account.
Pictures and text can be copied from your original Tumblr posts and saved to your computer's hard drive or clipboard. When you've collected all the posts you want to upload, create new posts on Tumblr and copy the content into your new blog. Click the gear icon on the new post you're creating to set a date for the post; you can use this to make your posts appear as if they were uploaded on the same day they were uploaded to your original Tumblr blog.
If This, Then That
One quick way to move old Tumblr posts between accounts is to use a service called IFTTT (link in Resources). On it, create rules using triggers: the first trigger for Tumblr post transfer should be liking a public post; the secondary trigger should be creating a new post of a certain type. Since IFTTT can do only one type of post, whether text, audio, video or some post-type Tumblr offers, the most efficient way to use IFTTT to quickly transfer posts is to set up a rule with one type of post, and then like all the posts on your old blog that are that type. You can then remove that rule and create a new one with a different post type.