This study examines the information-seeking behaviour of members of State Houses of Assembly in North-West Nigeria and its implications for legislative effectiveness and evidence-based lawmaking. Legislators require reliable, timely, and relevant information to perform their core functions of lawmaking, representation, and oversight. However, in many developing democracies, legislative decision-making is often constrained by weak institutional information systems and overreliance on informal sources. Using Wilson’s (1999) Model of Information Behaviour as the theoretical framework, the study adopted a descriptive survey design involving 202 legislators across seven states in the North-West geopolitical zone of Nigeria. Data were collected using a structured questionnaire and analyzed using descriptive statistics, chi-square tests, and multiple regression analysis. Findings reveal that legislators predominantly rely on informal information sources such as legislative aides, colleagues, mass media, and internet platforms, while formal sources such as legislative libraries and academic databases are significantly underutilized. Major barriers to effective information access include inadequate ICT infrastructure, time constraints, limited research support, and political bias. The study further establishes a significant positive relationship between information-seeking behaviour and legislative effectiveness (R² = 0.45, p < 0.001), indicating that improved access to and use of quality information enhances legislative performance. The study concludes that weak institutional information systems undermine evidence-based lawmaking in North-West Nigeria. It recommends the establishment of functional legislative research units, digitization of legislative libraries, capacity building in ICT and information literacy for legislators, and stronger collaboration between State Houses of Assembly and academic institutions. Strengthening these systems is essential for improving the quality of governance and policy outcomes in the region