Marvel Comics icon Stan Lee died due to cardiac arrest, respiratory and congestive heart failure, according to his death certificate from the Los Angeles Department of Health.
The certificate was obtained by people.com.
Lee suffered from aspiration pneumonia. In late February, he revealed he was battling pneumonia, explaining to TMZ that he had to cancel several appearances because of his illness.
The release of his death certificate comes two weeks after Lee died on November 12 at the Cedars-Sinai Medical Centre here. He was 95.
On November 16, Lee's POW! Entertainment said the comic book legend was laid to rest "in accordance to his final wishes".
"As we all continue to process our feelings of loss at the passing of a true legend, many are asking if there will be a memorial in Stan's honour," the company said in a statement.
"Stan was always adamant that he did not want a large public funeral, and as such his family has conducted a private closed ceremony in accordance with his final wishes. Our thoughts and prayers continue to be with them."
Lee was credited with co-creating some of the popular superheroes like Spider-Man to Black Panther. But it wasn't until years later that he became the public figurehead and face of Marvel Comics.
He often made appearances at comic book conventions and lectured at colleges. Lee continued to play an important role as Marvel transitioned into television during the 1980s, serving as narrator on animated series like "Incredible Hulk".
Lee also made cameos in a total of 26 movies, beginning with "The Trial of the Incredible Hulk" in 1989 and ending with 2018's "Venom".
Before his death, Lee completed cameos in several upcoming films, including one for Disney's "Ralph Breaks the Internet".
Lee is survived by his daughter Joan Celia "J.C." Lee.