Abstract Background Anxiety is highly prevalent during pregnancy and postpartum, and access to treatment can be difficult due to a range of barriers (e.g., time, distance, and service availability). Online treatments have the potential to circumvent these barriers and may, therefore, be beneficial for the perinatal population. The present study leveraged qualitative methods to understand participants’ perspectives on their use of a six-module online self-directed Cognitive Behavioral Therapy (CBT) program for perinatal anxiety as part of a randomized controlled trial. Methods A mixed qualitative method design was used for this study. A total of 95 perinatal women were randomized to an intervention or waitlist control condition for an online self-directed program (Overcoming Perinatal Anxiety; OPA). Both waitlist and intervention participants provided open-ended feedback on each module via online surveys. A subset of individuals (n = 20) assigned to the intervention condition completed a virtual qualitative interview about their experiences using the program. Data obtained from open-ended survey questions and qualitative interviews were analyzed using Conventional Content Analysis (open-ended survey) and Reflexive Thematic Analysis (interviews). Results Open-ended survey data were categorized into three themes, with associated sub-themes: User experience (subthemes: accessibility and modality), Perceptions of content (sub-themes: validating, informative, hopeful, anxiety-inducing, emotionally “heavy”, and helpful), and Barriers to program engagement (subthemes: lack of time and energy, technical difficulties, challenging and external factors). Qualitative interview data were categorized into the following main themes, with associated subthemes: Tensions in engaging with the self-directed program (subthemes: connecting and multi-tasking, “finding the time,” module length and pacing, pen to paper, and “thanks for the reminder but don’t rush me”), “I’m not alone,” (subthemes: relating to the content, sharing anxiety with “inner circle,” and voicing a desire to connect with other “moms feeling the same way”), and “I’m managing my anxiety” (subthemes: “understanding my anxiety,” using “strategies to help with my anxiety,” “taking time for myself,” and moving forward). Conclusion Findings highlight that online self-directed treatment can be an acceptable and feasible option for perinatal anxiety. Findings show promise for the scalability of OPA to improve access to psychological treatment for perinatal people experiencing anxiety. Trial registration Clinical Trial Identifier: NCT04844138 (clinicaltrials.gov). Trial registration submitted: [April 5, 2021] accepted: [April 14, 2021].