Objective: The present research assessed the psychometric validity of the Implicit Theories of Intelligence Scale (ITIS). Also, the current study examined how growth mindset is associated with academic achievement and engagement. Methods: A sample of 538 Filipino undergraduate students with a mean age of 20.9 (SD = 2.2) took part in the study. Confirmatory factor analysis was used for the within-network construct validity while correlation analysis for the between-network construct validity. Structural equation modelling was utilised in analysing the influence of growth mindset on academic outcomes. Results: The results indicate that the scale had good within-network validity, supporting its two-dimensional structure. The between-network construct validation revealed that growth mindset was associated with failure-is-enhancing mindset while fixed mindset was correlated with failure-is-debilitating mindset. Then, structural equation modelling revealed growth mindset predicted higher self-reported achievement through engagement. Conversely, fixed mindset was not associated with engagement, but it had a negative effect on achievement. Conclusion: The present study provided evidence that the ITIS is a valid and reliable measure of implicit theories of intelligence among Filipino undergraduate students. Growth mindset also predicted greater achievement through engagement.