Justina Machado as Penelope Riera Alvarez, a United States Army Nurse Corps and mother of Alex and Elena. She works as a nurse for Dr. Leslie Berkowitz. After coming back from army service, she joins a therapy group to help her with her depression and anxiety. In the first season she separates from her husband Victor and starts dating Ben. Later she breaks up with Ben after Victor 's visit for Elena 's quinceañera. In season two Penelope decides to go back to school to become a nurse practitioner. She begins dating an Army Veteran, now EMT Max Ferraro, but breaks up with him after finding out he wanted children of his own, and decides to let him find that chance with someone else, as she believes that she is too old for another child, and has two children of her own. Todd Grinnell as Dwayne Schneider, the rich landlord of the building. He is a close friend of the family and Penelope 's best friend. Schneider is frequently having one - night stands with different women. Often in the series he talks about having multiple stepmothers and how dysfunctional his family was, while also occasionally discussing his history of addictions. He is Canadian and after years of having a green card decides to become a US citizen. Isabella Gomez as Elena Maria Alvarez Riera Calderón Leytevidal Inclán, the activist and feminist teenage daughter of Penelope. After dating Josh, a classmate, and watching gay porn, she discovers that she is a lesbian and comes out to her family. The news does n't sit well with her father, which upsets Elena. In season two she finds a love interest and founds a Gay - Straight Alliance club at her Catholic School. Marcel Ruiz as Alejandro "Alex '' Alberto Alvarez Riera Calderon Leytevidal Inclan, the son of Penelope. He wants to gain popularity at school and is part of the baseball team. He starts a school project about Cuba. In season two he begins working during the summer at Dr. Berkowitz 's office. Rita Moreno as Lydia Riera, a faithful Cuban, Penelope 's mother and grandmother of Elena and Alex. She fled Cuba after Castro seized power. She was a dancer and a performer back in the day. Over the course of the season, she develops a relationship with Dr. Berkowitz. Stephen Tobolowsky as Dr. Leslie Berkowitz, Penelope 's boss and Lydia 's love interest.
who plays the boy in one day at a time
Marcel Ruiz