The construction industry continues to face challenges in improving operational efficiency and resource utilization. Lean construction offers a systematic approach to addressing these inefficiencies by optimizing processes and minimizing waste. Despite the growing adoption of lean practices in healthcare and manufacturing sectors, their practices in the Philippine private construction industry remain limited. This research explores the effect of five lean practices, namely continuous improvement, leadership support, long-term thinking, waste elimination, and focus on the final user, on process effectiveness in a private construction firm. This study employed a descriptive causal research design and utilized a questionnaire that targeted 120 rope access technicians. The study implemented a total enumeration sampling. Regression analysis revealed that all five lean construction practices significantly affect process effectiveness, with long-term thinking showing the strongest positive effect. Remarkably, waste elimination had a negative effect, suggesting implementation challenges. The study recommends targeted training, pilot testing, and improved coordination to align waste reduction with project goals. Embedding strategic planning, developing leadership, and incorporating client feedback are important steps in realizing the full potential of lean construction.