Depression and marital satisfaction have a reciprocal cause-and-effect relationship. Thus, couple relationships should be considered to maximize the effectiveness of couple-oriented interventions for depression. Moreover, developing culturally tailored couple-oriented interventions is critical for improving cultural acceptability and enhancing the perceived effectiveness of the interventions. A new culturally tailored MindGuide Couple intervention was developed to prevent Korean middle adulthood depression and enhance couple relationships using intervention mapping. This feasibility study used a single-arm, pre- and post-test, and 2-month follow-up design to explore the reach, acceptability, and preliminary effectiveness of this preventive intervention. Reach was assessed by recruitment, retention, and completion rates; acceptability was measured based on helpfulness, suitability, and satisfaction; and preliminary effectiveness was measured by depression (CES-D), positive and negative affect (PANAS), satisfaction with life (SWLS), couple satisfaction (CSI), and healthy relationship between spouses (FRAS). Fifteen middle-aged couples participated in four psychoeducational and asynchronous online modules and four synchronous coaching sessions via videoconferencing for 5-7 weeks. Data were analyzed using descriptive statistics and repeated measures with analysis of variance. With a 94.1% completion rate, the participants demonstrated high satisfaction with the online coaching blended intervention and reported that it was helpful and easy to use. Both husbands and wives showed significant differences over time in depression, couple satisfaction, and healthy relationships between spouses. This feasibility study demonstrated the successful reach, acceptability, and potential effectiveness of this preventive intervention. Additionally, we suggest the importance of culturally tailored and online coaching blended couple-oriented intervention for preventing depression and promoting healthy couple relationships.