Rooney Mara goes casual in sweats with fiancé Joaquin Phoenix and their baby boy River

Rooney Mara became a mom last year when she and fiancé Joaquin Phoenix welcomed their first child.

And the two-time Academy Award nominee is enjoying some quality family time during the ongoing lockdown.

She went grayscale Thursday in some cozy chic sweats, as she stepped out with Joaquin, their baby boy River and their dog Oskar, visiting her sister Kate Mara in Los Angeles.

Family outing: Rooney Mara went grayscale Thursday in some cozy chic sweats, as she stepped out with fiancé Joaquin Phoenix, their baby boy River and their dog Oskar, visiting her sister Kate Mara in Los Angeles

The 35-year-old donned a black sweatshirt with two-tone grey sleeves, complemented with black pants and black creepers.

She sported a white face mask and toted a navy blue diaper bag over her shoulder, while carrying Oskar to the car.

Joaquin, 46, rocked a black LA Animal Save hoodie with matching pants, beanie, wayfarers and black Nike trainers.

He took precautions against COVID-19 in a black face mask, as he carried River, covered up in his car seat. 

Cozy chic: The 35-year-old donned a black sweatshirt with two-tone grey sleeves, complemented with black pants and black creepers

Cozy chic: The 35-year-old donned a black sweatshirt with two-tone grey sleeves, complemented with black pants and black creepers

Back in black: Joaquin, 46, rocked a black LA Animal Save hoodie with matching pants, beanie, wayfarers and black Nike trainers

Back in black: Joaquin, 46, rocked a black LA Animal Save hoodie with matching pants, beanie, wayfarers and black Nike trainers

The couple welcomed their son last fall, naming him after Joaquin’s late brother River Phoenix, who died at 23 years old in 1993. 

Director Victor Kossakovsky spilled the beans at the 2020 Zurich Film Festival in September, after a screening of the film Gunda, on which Joaquin served as executive producer.  

He slipped in the news during a Q&A, after he was asked how he got the new dad involved in the film: ‘He just got a baby by the way… A beautiful son called River.’ 

New addition: The couple welcomed their son last fall, naming him after Joaquin's late brother River Phoenix, who died at 23 years old in 1993 (pictured in February, 2020)

New addition: The couple welcomed their son last fall, naming him after Joaquin’s late brother River Phoenix, who died at 23 years old in 1993 (pictured in February, 2020)

Big news: Director Victor Kossakovsky spilled the beans at the 2020 Zurich Film Festival in September, after a screening of the film Gunda, on which Joaquin served as executive producer: 'He just got a baby by the way... A beautiful son called River' (pictured in May, 2017)

Big news: Director Victor Kossakovsky spilled the beans at the 2020 Zurich Film Festival in September, after a screening of the film Gunda, on which Joaquin served as executive producer: ‘He just got a baby by the way… A beautiful son called River’ (pictured in May, 2017)

Growing family: The animal rights advocates live in the Hollywood Hills with their two dogs Soda and Oskar, and their engagement was confirmed in July of 2019, a few months after she was first spotted wearing her engagement ring (pictured in November, 2013)

Growing family: The animal rights advocates live in the Hollywood Hills with their two dogs Soda and Oskar, and their engagement was confirmed in July of 2019, a few months after she was first spotted wearing her engagement ring (pictured in November, 2013)

River died at the peak of his career, with memorable roles in Stand By Me (1986), Indiana Jones and the Last Crusade (1989), and Gus Van Sant’s My Own Private Idaho (1991) already under his belt. 

Joaquin opened up about River’s legacy in a rare interview with Anderson Cooper for 60 Minutes in September.

The Joker star said: ‘I feel like in virtually every movie that I made, there was a connection to River in some way. And I think that we’ve all felt his presence and guidance in our lives in numerous ways.’      

Gone too soon: River died at the peak of his career, with memorable roles in Stand By Me (1986), Indiana Jones and the Last Crusade (1989), and Gus Van Sant's My Own Private Idaho (1991) already under his belt

Gone too soon: River died at the peak of his career, with memorable roles in Stand By Me (1986), Indiana Jones and the Last Crusade (1989), and Gus Van Sant’s My Own Private Idaho (1991) already under his belt

Beloved brother: Joaquin opened up about River's legacy in September: 'I feel like in virtually every movie that I made, there was a connection to River in some way. And I think that we've all felt his presence and guidance in our lives in numerous ways' (pictured in 1985)

Beloved brother: Joaquin opened up about River’s legacy in September: ‘I feel like in virtually every movie that I made, there was a connection to River in some way. And I think that we’ve all felt his presence and guidance in our lives in numerous ways’ (pictured in 1985)

They subtly confirmed the news of their firstborn’s arrival in November, when they mentioned him in an op-ed for People about the migrant children crisis. 

Rooney began dating her Her (2013) costar in late 2016, and they later starred together in Don’t Worry, He Won’t Get Far on Foot and Mary Magdalene, both of which premiered in 2018. 

The animal rights advocates live in the Hollywood Hills with their two dogs Soda and Oskar, and their engagement was confirmed in July of 2019, a few months after she was first spotted wearing her engagement ring.

Onscreen romance: Rooney began dating her Her (2013) costar in late 2016, and they later starred together in Don't Worry, He Won't Get Far on Foot and Mary Magdalene, both of which premiered in 2018

Onscreen romance: Rooney began dating her Her (2013) costar in late 2016, and they later starred together in Don’t Worry, He Won’t Get Far on Foot and Mary Magdalene, both of which premiered in 2018