"Our actions are out of love and hope for our community," D'Onofrio wrote in a blog post.
"There are no shortage of sites on the internet that feature adult content."
The decision to purge porn from Tumblr was made after "serious thought" regarding standards in the blogging community, according to the chief executive.
"Posts that contain adult content will no longer be allowed on Tumblr, and we've updated our Community Guidelines to reflect this policy change," D'Onofrio said.
The new rules prohibit users from uploading "real-life human genitals or female-presenting nipples", but artistic representations may still be allowed.
D'Onofrio maintained that Tumblr will strive to balance allowing conversation about topics such as sex and relationships with banning porn, and noted there are likely to be stumbles.
Child porn was already against Tumblr guidelines.
"Posting anything that is harmful to minors, including child pornography, is abhorrent and has no place in our community," D'Onofrio said.
"We've always had and always will have a zero tolerance policy for this type of content."
Tumblr's applications for Apple devices were shut out of the App Store last month after child sexual abuse material was found on the platform.
Tumblr uses an industry database to filter content being uploaded, but child porn material that had not yet been added to the database made it onto the platform, the company said.
The offending content was removed as soon as it was discovered in a routine audit, according to Tumblr.
D'Onofrio took over as chief of Tumblr from founder David Karp late last year.
Karp's departure from the company came a few months after Verizon bought parent-company Yahoo in a $4.5 billion deal.
Karp founded Tumblr in New York in early 2007 as a platform where people could share writing and short-form media. Now, Tumblr hosts some 417 million different blogs.
Yahoo acquired Tumblr in May 2013 for $1.1 billion, as part of an effort to better connect with younger online users