Internet-based interventions have proven to be effective for the treatment of depression in different samples, but evidence from the Middle East and North Africa (MENA) region is scarce. The aim of this study was to investigate the acceptance and efficacy of an internet-based cognitive behavioural writing intervention for Arabic-speaking participants with depression living in the MENA region. A total of 259 participants (167 female, age in years: M = 25.58, SD = 6.39) with depressive symptoms indicative of clinical relevance were randomly allocated to a treatment group (TG; nTG = 128) or a waitlist control group (WG; nWG = 131). The TG received an internet-based intervention over a 6-week period. The primary outcome was depressive symptoms, and secondary outcomes were anxiety and quality of life (QoL). T-tests with change scores from pre- to post-treatment were used for data analyses. Intention-to-treat (ITT) as well as completer analyses were calculated. The ITT analysis revealed significant differences between the TG and WG in depression (T257 = −4.89, p < 0.001, d = 0.70) and QoL (T257 = 3.39, p < 0.001, d = 0.47). Significant differences regarding anxiety symptoms (T257 = 3.25, p < 0.05, d = 0.53) were identified for the completer sample. The general dropout rate was 39.9%. The results indicate the feasibility and efficacy of an internet-based cognitive behavioural writing intervention in adults from Arabic-speaking countries. The development and implementation of such interventions can be used to improve access to psychological help and adequate treatment.