Purpose:　The　nature　of　public-private　partnership　(PPP)　markets,　industry　competition,　and　organizational　embeddedness　(e.g.　collaboration　experience),　significantly　influence　how　private-sector　organizations　in　PPP　establish　relational　ties　and　create　project　networks　during　the　PPP　procurement　phase.　This　necessitates　a　multi-level　perspective　to　unveil　the　relationship　mechanisms　and　behaviors　of　organizations　in　PPP　at　different　levels.　This　study　aims　to　analyze　the　industry,　clustering,　and　local　characteristics　of　organization　relationships　using　a　longitudinal　dataset　of　PPP　transportation　projects　sourced　from　the　National　PPP　Integrated　Information　Platform　(NPPPIIP).　Design/methodology/approach:　This　study　adopts　a　multi-level　analytical　approach,　encompassing　whole-network,　clustering-network,　and　local-network　levels,　to　explore　the　mechanisms　of　organizational　relationships　and　behavioral　patterns　within　collaboration　networks　among　private-sector　organizations.　Findings:　The　results　indicate　that　(1)　organizational　relationships　within　PPP　unfold　spontaneously　over　time,　driven　intrinsically　and　collectively,　devoid　of　prior　planning,　control,　external　direction,　or　imposed　order　at　the　industry　level,　with　the　evolution　of　four　collaboration　types　elucidating　the　emergence　of　self-organizing　networks;　(2)　super　enterprises　exhibit　exceptional　breadth,　brokerage,　and　ego　abilities,　and　relationship　patterns　are　governed　by　the　effects　of　geographic　proximity　and　preferential　attachment　at　the　clustering　level;　and　(3)　local　relationship　patterns　are　characterized　by　embeddedness　mechanisms,　including　relational　and　structural　aspects.　Originality/value:　The　multi-level　analysis　framework　enhances　our　understanding　of　organization　interactions　in　the　PPP　procurement　phase,　breaking　away　from　the　traditional　social　network　analysis　(SNA)　at　both　the　network-centric　and　ego-centric　levels.　Overall,　the　insights　are　valuable　for　policymakers　designing　improved　tendering　processes　and　for　PPP　private-sector　organizations　seeking　a　comprehensive　overview　of　competition　and　collaboration　in　the　transportation　infrastructure　sector.　©　2025,　Emerald　Publishing　Limited.