"I thought at the time this was going to be a very good career move. Um, it wasn't," he said.
23 years after its release, Batman & Robin remains one of the most controversial films in the Batman canon.
Director Joel Schumacher has since offered fans an apology.
The prolific director was at the helm for two Batman films during the 90s: Batman Forever, which saw Val Kilmer as the masked crusader, and Batman & Robin, in which ER star George Clooney tried his luck as a superhero.
The former received mixed reviews, while the latter was savaged by critics and struggled at the box office.
"Look, I apologise. I want to apologise to every fan that was disappointed because I think I owe them that," he said in an interview with Vice.
The director said that, with the benefit of hindsight, he can see he should have left the franchise after the success of 1995's Batman Forever.
"You know, I just knew not to do a sequel. If you get lucky, walk away. But everybody at Warner Brothers just expected me to do one."
"Maybe it was some hubris on my part. I had a batting average of 1000, so I went from falling down a bit after Lost Boys, to a kind of a genius with The Client, a big blockbuster with Batman Forever, then had great reviews with A Time to Kill, so my batting average was good.
"I never planned on being, that dreadful quote, 'a blockbuster king' because my other films were much smaller and had just found success with the audience and not often with the critics, which is really why we wrote them.
And then after Batman & Robin, I was scum. It was like I had murdered a baby," he recalled.
The film has an 11 percent approval rating on review aggregating website Rotten Tomatoes, who summarise that it is "a frantic and mindless movie that's too jokey to care much for."
It certainly took some time for the Batman franchise to recover - it would be eight years before another big-screen instalment in the series, with 2005's Christopher Nolan-directed Batman Begins launching the Christian Bale vision of the superhero that lives on today.