Purpose of study: This study examined the effectiveness of Public–Private Partnerships (PPPs) in enhancing disaster preparedness in Nairobi County, Kenya (2019–2025), focusing on resource mobilisation, inter-sectoral collaboration, and implementation challenges within urban disaster management. Methodology: A descriptive mixed-methods design was employed. Data were collected from 132 respondents via structured questionnaires, 15 key informant interviews, and four focus group discussions involving public officials, private firms, NGOs, and community members. Quantitative data were analysed using SPSS (descriptive statistics), while qualitative data underwent thematic analysis, enabling triangulation of findings. Findings: PPPs significantly improved resource mobilisation (M=4.34), technological innovation (M=4.26), early warning systems (M=4.21), logistics (M=4.17), and community awareness (M=4.10). Collaborative approaches reduced duplication (M=4.13) and improved response times (M=4.01). However, effectiveness was severely constrained by the absence of a formal policy framework (M=4.36), bureaucratic decision-making (M=4.22), mutual distrust between sectors (M=4.18), inadequate monitoring and evaluation (M=4.06), and insufficient financial incentives (M=3.89). Qualitative data revealed that partnerships remained largely ad hoc, episodic, and event-driven rather than institutionalised, with community members reporting exclusion from planning processes and coordination mechanisms described as poorly structured (M=3.78). Conclusion: PPPs hold significant unrealised potential for disaster preparedness in Nairobi County. Structured formalisation through binding agreements, dedicated coordination units, incentive mechanisms, and trust-building measures is essential. Without addressing policy gaps and institutional weaknesses, PPPs will remain underperforming mechanisms for building urban disaster resilience.