Prenatal tobacco use is a pressing public health problem, placing individuals who use and their infants at greater risk of poor health outcomes relative to other populations. Co-use of tobacco and cannabis during pregnancy is also common and may hinder prenatal smoking cessation and postpartum tobacco abstinence. Depressive symptoms represent a modifiable factor related to discrimination, prenatal tobacco, and prenatal cannabis use that can be addressed to promote perinatal cessation and prevent relapse. Effective perinatal tobacco and cannabis use cessation interventions created in partnership with populations likely to use are needed. Accordingly, the proposed project is designed to achieve the following aims: (1) Guided by a community collaborative, we propose to conduct formative research on the experiences of pregnant women who use cannabis and tobacco, to contextualize the role of depressive symptoms in prenatal dual use. We will co-create an interview guide; conduct interviews with 35 pregnant and parenting females who engage(d) in dual use and experienced prenatal depressive symptoms to determine the relationship among symptoms and tobacco and cannabis use, quit attempts, withdrawal, and relapse. We will code and evaluate themes from these interviews with the collaborative. (2) Guided by a community collaborative and using an intervention mapping approach, we will develop an intervention targeting prenatal depressive symptoms for prenatal tobacco and cannabis smoking cessation. (3) Guided by a community collaborative, will conduct a single group, proof of concept feasibility trial of the new intervention designed to address prenatal depressive symptoms to encourage tobacco and cannabis cessation. Together, we will assess needs, choose behavioral targets, and review the feasibility and acceptability of the novel intervention to prepare for future evaluation of efficacy. Although there are interventions addressing perinatal depressive symptoms, extant interventions may not be appropriate or effective for pregnant people who use both cannabis and tobacco. The proposed study amplifies the voices of pregnant women with higher rates of prenatal depressive symptoms and dual prenatal tobacco and cannabis use. Thus, the project will provide data critical for a novel intervention to reduce prenatal co-use of tobacco and cannabis.