This study investigates the determinants of green investment among LQ45 companies, a leading stock index in Indonesia. Grounded in the resource-based view and stakeholder theory, we hypothesize that firm-specific resources and the pressure from stakeholders will influence green investment. Employing panel data from 2018 to 2023, we utilize a random effects model to analyze the impact of firm size, profitability, leverage, and asset turnover on green investment, while examining the moderating role of tax policy. Our findings support the hypotheses, indicating that larger, more profitable firms with higher asset turnover are more likely to engage in green investments. Furthermore, tax incentives significantly enhance the positive relationship between firm characteristics and green investment. These results highlight the importance of both internal firm capabilities and external pressures in driving sustainable practices. Policymakers should consider implementing targeted tax incentives, providing access to green finance, and fostering a supportive regulatory environment to encourage greater green investment among Indonesian firms.