The business environment in Tanzania has undergone significant structural reforms, yet persistent and novel constraints continue to affect enterprise growth and sustainability. A nuanced, longitudinal understanding of these challenges from the perspective of local entrepreneurs remains underdeveloped. This study aimed to diagnose the enduring and emerging obstacles faced by Tanzanian businesses, identifying their perceived severity and evolution to inform targeted support mechanisms. A qualitative, multi-method design was employed, incorporating in-depth, semi-structured interviews with business owners and managers, and focus group discussions with sectoral associations. Purposive and snowball sampling secured a diverse sample across manufacturing, trade, and services in three major urban centres. Thematic analysis was conducted using NVivo software. Analysis identified a dominant theme of 'regulatory unpredictability', where frequent, non-consultative changes to fiscal and compliance rules were cited by approximately 70% of participants as a primary constraint. Emerging challenges centred on digital infrastructure gaps and climate-related supply chain disruptions, which were particularly acute for agricultural value chains. The business landscape is characterised by a complex interplay of long-standing institutional hurdles and new, systemic vulnerabilities. Addressing these requires moving beyond generic policy prescriptions to context-specific, adaptive interventions. Policymakers should establish a permanent, public-private business environment monitoring council. Development partners are advised to shift support towards building adaptive resilience, particularly for climate-vulnerable sectors and digital integration. Business environment, qualitative diagnostic, regulatory unpredictability, enterprise constraints, Tanzania This paper provides a novel, longitudinal diagnostic framework that distinguishes between enduring and emergent business challenges, offering a granular evidence base for prioritising policy and programme interventions in similar contexts.