Background: Poor oral health severely affects quality of life, disproportionately impacting individuals with low socioeconomic status due to limited or partial dental coverage. In Barcelona, many people face barriers to dental care. In 2018, the Barcelona City Council launched a free dental service for economically disadvantaged populations to improve access to essential treatments. Objective: This study evaluates Barcelona’s Social Dentistry Service regarding its scope, patient profiles, satisfaction, and perceived impact from professional and patient perspectives. Methods: We conducted a non-experimental, mixed-methods evaluation involving patients and dental professionals. Data were obtained through interviews with both groups, an online questionnaire for professionals, and analysis of service records from 2018 to 2022. Results: From November 2018 to December 2022, the service provided 39,557 visits to 4499 individuals (4344 adults; 155 children). Professionals strongly endorsed the service, stressing its necessity and positive impact. Patients reported high satisfaction, citing accessibility, effective treatments, and professional quality as strengths, while also expressing concerns about gaps in coverage and future availability. Both groups reported benefits beyond oral health, including improved physical and mental well-being, social relationships, and self-care. Patients highlighted pain relief, increased self-esteem, quality of life, and motivation for social participation. Conclusion: The Social Dentistry Service markedly improves patients’ oral health, psychological well-being, and social integration. Universal dental coverage policies are needed; meanwhile, similar interventions should be sustained and expanded in areas lacking coverage.