Purpose: The study examined the effect of project planning practices on the success of infrastructure projects in Nigeria, focusing on project scheduling, budgeting and cost planning, and risk management combined with stakeholder engagement. The study sought to determine how these planning practices influence timely completion, cost performance, and overall project success.

Methodology/Design: A quantitative research design was adopted, using a survey approach. Data were collected from 400 professionals involved in infrastructure projects, including project managers, engineers, architects, quantity surveyors, and government officials. Structured questionnaires were employed, and data were analyzed using descriptive statistics, regression analysis, and structural equation modeling (SEM) via SPSS and SmartPLS. Reliability and validity were confirmed through Cronbach’s alpha and factor analysis.

Findings: The results indicated that project scheduling practices significantly improved timely completion (β = 0.42, p < 0.01), budgeting and cost planning positively influenced cost performance (β = 0.38, p < 0.01), and the combination of risk management and stakeholder engagement enhanced overall project success (β = 0.46, p < 0.01).

Implications: The findings underscore the importance of systematic project planning, highlighting that structured scheduling, financial planning, and integrated risk/stakeholder management are critical for infrastructure project success in Nigeria.