<p>Although iterative development concepts predate the 2001 Agile Manifesto, the ideas outlined in the manifesto significantly transformed project management, introducing a renewed approach. However, challenges persist, particularly regarding the criteria for selecting both a suitable project management approach (traditional, agile, or hybrid) and a corresponding software development life cycle (SDLC) model. This Systematic Mapping Study (SMS) analyzes existing literature to identify evidence on complexity factors that guide the selection of project management strategies and, subsequently, the appropriate SDLC model. While several complexity factors are documented, a lack of integrated frameworks and guiding criteria remains. Different SDLC models can be applied within each approach, yet their selection often relies heavily on the project manager’s experience due to the absence of formal guidance. The study highlights the need for research efforts aimed at bridging this gap and informing decisions through evidence-based practices. The mapping identified 67 primary studies, with a predominance of agile-oriented research and limited presence of formal frameworks guiding the combined selection of project strategies and SDLC models. The analysis revealed a diverse set of technical and environmental complexity factors, and a lack of systematic guidance in the literature. Based on this evidence, the study proposes a preliminary taxonomy to support future framework development and improve decision-making in practice.</p>