Background: Attention-Deficit/Hyperactivity Disorder (ADHD) in adults, particularly women, is frequently underdiagnosed and understudied, especially in culturally diverse populations. Self-criticism, shame, and attachment difficulties often co-occur with ADHD and may complicate treatment. While Cognitive Behavioural Therapy (CBT) is considered the recommended intervention, it may not fully address affect regulation difficulties or interpersonal distress. Compassion-Focused Therapy (CFT) offers an alternative, emotion-focused approach that integrates attachment theory and self-compassion. This case study explores the impact of a culturally adapted CFT intervention for a Latin American female adult with ADHD, low mood and attachment-related difficulties. Methods: A single-case AB design was employed with a 16-session intervention based on a CFT protocol adapted to include cultural elements such as familismo. The client, a late-diagnosed ADHD adult experiencing persistent low mood and self-criticism, completed outcome measures at three time points (pre-, mid-, and post-intervention). Measures included the PHQ-9, GAD-7, WSAS, ECR-S, FOCS, and CEAS-SC. The intervention focused on mindfulness, imagery, compassion-based practices (e.g., multiple selves, compassionate letter writing), and culturally tailored visualizations. Results: The client demonstrated clinically meaningful reductions in depressive symptoms and functional impairment. Attachment-related avoidance decreased, and fears of self-compassion showed improvement by mid-treatment. Although changes in compassionate engagement were modest, qualitative feedback highlighted the value of compassion practices in eliciting true affect and reducing self-criticism. Cultural adaptations, particularly the use of collective imagery and familismo-oriented content, were reported as highly beneficial. Discussion: The findings suggest that CFT may be a promising intervention for adults with ADHD who present with shame, self-criticism, and complex attachment histories. The case emphasizes the importance of cultural sensitivity, especially in underrepresented populations. Interventions that integrate imagery, compassion, and interpersonal processing may be more effective than cognitively focused approaches for clients prone to demonstrating false affect and true cognition. Conclusion: This case supports the potential utility of culturally adapted CFT for Latin American adults with ADHD and attachment-related distress. Further research with larger and more diverse samples is needed to explore generalizability and enhance intervention design for cross-cultural clinical populations.