Purpose This study empirically investigates the impact of information technology(IT) investments on the financial and non-financial performance of a manufacturing firm. We examined the interaction effects of IT investments and strategic applications levels of information systems(IS). This study also demonstrated the three-way interaction effects of IT investments, levels of IS strategic applications, and perceived environmental uncertainty(PEU). Design/methodology/approach For this study, empirical data were collected from 98 manufacturing firms with the structured questionnaires. The data were analyzed with multiple regression models, and partial derivatives were utilized to identify the directions of the impact. Findings From the empirical results, it was found that when both the levels of IS strategic applications and the degrees of IT investments are high, the ratios of the costs of goods sold to total sales(RCGS) and the labor costs to total sales(RLCS) are decreased, as it were, the performance of a firm is improved. However, it was observed that when the levels of strategic IS are low, the high degrees of IT investments do not contribute to the improvement of a performance. The results showed that when the levels of strategic IS are high, the high degrees of IT investments incur the high RSAE not low RSAE. When PEU is considered, the empirical results showed that under the low degrees of PEU, the IT investments under high levels of strategic IS applications (strategic IT investments) improve the performance, as it were, low RCGS, and high degrees of perceived financial and non-financial performance. However, under high PEU, it was observed that high degrees of strategic IT investments do not increase the performance. When PEU is high, the strategic IT investments reduce RSAE, and under low PEU, RSAE is increased.