Social work clients often face complex financial difficulties. To address this, we developed FinSoc, a financial social work intervention designed to improve financial literacy, strengthen economic self-efficacy and reduce financial anxiety among parents in Finland. This pilot randomized controlled trial aimed to evaluate the feasibility, acceptability and preliminary effectiveness of the intervention. Altogether, 30 social work clients participated in the study and were randomly assigned to either the intervention or a waitlist control group. Data were collected at three time points: before the intervention, immediately after and at a 3-month follow-up. Additionally, qualitative interviews were conducted with both participants and professionals implementing the intervention. Of the 55 individuals assessed for eligibility, 30 enrolled in the study (54.5%), and 80% completed the 3-month follow-up. Acceptability was high: 13 of the 14 clients (92.9%) who completed all sessions rated the intervention as useful, and professionals viewed it as beneficial in supporting clients' financial capabilities. Although the group × time interactions for financial literacy, financial anxiety and economic self-efficacy did not reach statistical significance, the findings may nevertheless suggest some potential for effectiveness. The study was prospectively registered (ISRCTN 38586825).