The cumulative effects of adversity and unhappiness affect life satisfaction and quality of life in the growing older adult population. Most of the interventions aimed at improving the health and quality of life of older adults have adopted a problem-oriented or weakness-focused approach. However, a positive or strengths-focused approach can also have a virtuous but more effective capacity to contribute to the well-being and life satisfaction of older adults. Therefore, the present study was conducted to investigate the effect of positive thinking training on improving resilience and life satisfaction among older adults. A randomized controlled trial was conducted on 100 older adults with simple random sampling. The intervention group received 90-min weekly sessions for eight weeks on positive thinking training through written homework for reflection, group discussion, and media. The data were collected using Ingram and Wisnicki Positive Thinking Questionnaire, Connor-Davidson Resilience Scale, and Tobin Life Satisfaction Questionnaire at baseline and one week and two months after the training. The collected data were analyzed using descriptive and inferential statistics in SPSS software 26. P values below 0.05 were considered statistically significant. Positive thinking training led to better thinking (p < 0.001), higher resilience (p < 0.001), and greater life satisfaction (p < 0.001). The study's findings showed the effectiveness of the positive thinking training approach in improving resilience and life satisfaction in older adults. It is recommended to evaluate the long-term outcome in populations with different social, economic, and cultural statuses in future studies.