This study investigates the factors impacting the achievement of adult learners in a technology certificate program on computer networks. We studied 2442 participants in 256 institutions. The participants were older than age 18 and were enrolled in the Cisco Certified Network Associate (CCNA) technology training program as 'non-degree' or 'certificate' students. Using a multilevel analysis, factors impacting adult learners' achievement were identified. The results of Hierarchical Liner Model (HLM) analysis demonstrated that work status, degree orientation, motivation, age, gender, and computer technical ability of the participants at the beginning of the program had impact on adult learner achievement. On the contrary to the past research, the analysis showed that adult learners with full-time jobs achieve more than adult learners with no full-time jobs. Additionally, the institutional level factors did not have any impact on achievement. Findings of this study provide important information for developing a framework that can guide research and practice in technology certificate programs.