The purposes of this study were to explore factors and indicators of life and career skills and to develop a life and career skills in the 21st century test for undergraduate students. This research employed a mixed-method study adopting an exploratory design: instrument development model to generate research tools. This study was divided into two phases; Phase 1 was to explore factors and indicators of life and career skills in 21st century, by using a qualitative method to analyze relevant documents; Phase 2 was the development of a life and career skills in 21st century test by adopting a quantitative method to collect data from students studying in 12 universities of the north-eastern region of Thailand via the test. In the second phase, the data were analyzed by descriptive statistics and Confirmatory Factor Analysis (CFA) Results revealed that the skills consisted of 6 factors and 35 indicators, and the test comprised 105 items. The quality of the test has been examined by five expertise, the reliability of all test items is acceptable, and all 6 factors demonstrated good construct validity. Factor loadings of six factors were 0.7940-1.7816. This study can be implemented to measure the life and career skills of undergraduate students in any university to obtain data for establishing a policy and plans for maximizing students' potential to achieve their careers and a happy living in 21st century after their graduation.