Nine months after her appearance in Hair, Diane meets comedian Woody Allen and is cast for his first Broadway play, Play It Again Sam. The two become romantically involved and their partnership quickly evolves into one of the most professionally prolific pairings in the business. Finding success as a stage actress, Diane makes the jump to film when she begins co-starring alongside Woody in several successful comedic ventures such as the celluloid version of Play it Again Same, Sleeper, and Love and Death, amongst others. In 1972 Francis Ford Coppola casts her in his epic mobster drama, The Godfather, as the much maligned Kay Corleone, wife of Michael Corleone (Al Pacino). She reprises the role in the 1974 sequel. Diane continues to act in films throughout the 70s, but skyrockets to stardom with in 1977 with two roles that captivate the nation. One is as the sexually promiscuous Theresa Dunn in Looking for Mr. Goodbar, and the other is as the titular role in Annie Hall, a loose parody of her relationship with Woody Allen. She is nominated for her first Academy Award, which she wins during the 1978 Oscar ceremony. She is also nomatined twice in the same category at the Golden Globes. Diane wins for Annie Hall. (It's hard competing against yourself!). As the decade comes to a close, Diane continues to work with Woody, garnering more critical acclaim in both Interiors and Manhattan. She again makes headlines after she becomes involved with Warren Beatty, who in turn, casts her along side him in his self-directed film Reds. In 1981, Diane is nominated for her second Academy Award for her performance as Louise Bryant in Reds.

The early 80s mark a stylistic change for Diane, as she seeks out more and more dramatic roles, such as Shoot the Moon, Mrs. Soffel, and Crimes of the Heart (adapted from Beth Henley's Pulitzer Prize winning play). Diane begins to venture into the directorial arena with 1987's Heaven, a documentary about well, heaven. Fittingly, she also begins to direct music videos, including Belinda Carlisle's Heaven is a Place on Earth. 1987 also saw Diane return to her comedic roots with her role as J.C. Wiatt, Tiger Lady, in Baby Boom. Around this time, Diane begins to date Al Pacino. The two find themselves onscreen together again in 1990's The Godfather Part III. Continuing her comedic revival, Diane co-stars as Steve Martin's better half in Father of the Bride (1991), and reteams with Woody Allen for 1993's Manhattan Murder Mystery. Next year, she is nominated for an Emmy award as Outstanding Lead Actress in a Miniseries or a Special for her title role in Amelia Earhart: The Final Flight. Diane joins Steve Martin again for the sequel to Father of the Bride in 1995, and in the same year, she directs her first full-length feature film, the critically acclaimed Unstrung Heroes. On Dicember 1995 Diane adopts a girl, Dexter. 1996 is a huge year for Diane, as she co-stars in the blockbuster hit The First Wives Club with Goldie Hawn and Bette Midler. She also acts alongside Meryl Streep in Marvin's Room and earns her third Academy Award nomination for her portrayal of cancer victim Bessie Wakefield.

Diane is back at the helm as director in 2000 with Hanging Up, in which she also stars alongside Meg Ryan and Lisa Kudrow. She also finds time to help out Warren Beatty for his film Town and Country. In 2001 Diane decides to give a brother to Dexter ad adopts Duke. 2003 Diane's upcoming film Something's Gotta Give pairs her with both Jack Nicholson and Keanu Reeves. For her role Diane won a Golden Globe and a nomination at the Academy Awards. 2004 Hot of the trails of her groundbreaking performance in Something's Gotta Give, Diane prepares for her next role in Callie Khouri's (screenwriter of Thelma & Louise) Mad Money. Goldie Hawn will produce. She will also play a dramatic role as a mother of a boy who commetted suicide in Da Vinci's Mother directed by Jim Sheridan (In America). Diane has also recently signed on to a family comedy written by Mark Perez and she will also play in The Family Stone, a movie for the Michael London Prodsa and for a CBS TV movie:Surrender Dorothy. She is also taking into consideration a role in a HBO tv serie.