Rock nailed the opening monologue with a skillful mix of social commentary and humour about racism in Hollywood, an issue that has dominated debates this awards season.
"Well, I am here at the Academy Awards, otherwise known as the White People Choice Awards. If they nominated hosts, I wouldn't even get this job," Rock quipped.
He also suggested that what was needed at this point is for the Academy to have black categories.
Rock addressed police violence against black community, saying "This year at the Oscars, things are gonna be a real different. In this year, in the In Memoriam package, it's just gonnna be black people who were shot by cops on the way to the movies."
Celebrities utilised the Oscar stage to voice their opinions on issues that are close to their hearts.
Breaking his Oscar jinx, when DiCaprio took to stage to accept his best actor trophy, the world expected him to look back at his cinematic journey but the 41-year-old star focused on climate change.
Smith won the best original song Oscar for "Writing's on the Wall" from the James Bond movie "Spectre" and he dedicated his first Academy Award to the LGBT community.
"I want to dedicate this to the LGBT community all around the world. I stand here tonight as a proud gay man. I hope we can stand all together as equals one day," he said.
"I am very lucky to be here tonight but unfortunately, many others haven't had the same luck...
Pakistani journalist-filmmaker Sharmeen Obaid-Chinoy won
best documentary short for "A Girl in the River: The Price of Forgiveness", which is about a survivor of an attempted honour killing in her country.
Sharmeen lauded the "brave men" and others who encourage women to study and progress in life.
This is the second win for Sharmeen, who previously bagged the Oscar in the same category in 2011 for "S aving Face", a documentary about an acid attack victim.
Tom McCarthy's real life-inspired drama "Spotlight", based on a group of reporters, who exposed the child sex abuse cases in Catholic church, won the best picture honour and the film's team took the opportunity to talk about the importance of investigative journalism.
"This film gave a voice to the survivors and the Oscar amplifies that voice which we hope will resonate all the way to the Vatican..," producer Michael Sugar said in his acceptance speech.
Best supporting actor winner Mark Rylance also spoke about the diversity issue that has marred the Academy since nominations last month.
On a hopeful note, Rylance said, "I think African-American actors are in a stronger position now thanks a lot to what Chris Rock has done tonight and what the activists who have been raising the issue around this awards ceremony have said," the British star said, adding that it is an issue for him that filmmaking is largely dominated by men.
