Structural　modal　parameters　are　crucial　for　monitoring　the　condition　of　bridges.　Operational　modal　analysis　(OMA)　has　garnered　great　attention　in　vibration-based　structural　health　monitoring　of　bridges　because　it　only　requires　vibration　measurements　from　multiple　sensors.　Slight　asynchronization　often　occurs　in　these　measurements　during　the　monitoring　process.　Applying　classical　OMA　methods,　such　as　the　natural　excitation　technique　(NExT)　combined　with　the　eigensystem　realization　algorithm　(ERA),　to　asynchronous　vibration　measurements　can　lead　to　significant　errors　in　modal　parameters.　To　address　this　issue,　this　study　proposes　a　modal　assurance　criterion　(MAC)-based　time　synchronization　technique　to　generate　reliable　synchronous　vibration　measurements　for　modal　identification.　The　MAC-based　method　takes　advantage　of　the　proportionality　of　modal　components　and　is　only　capable　of　detecting　nonsynchronized　issues　between　single-degree-of-freedom　(SDOF)　signals.　A　variational　mode　extraction　(VME)　technique　is　employed　to　iteratively　decompose　bridge　vibration　measurements　into　SDOF　components.　The　VME　technique　eliminates　the　need　for　artificially　predefining　the　number　of　modes,　which　was　required　in　many　signal　decomposition　techniques.　After　time　synchronization,　the　proposed　method　employs　the　NExT–ERA-based　automatic　OMA　method　for　modal　identification.　The　effectiveness　of　the　proposed　method　is　demonstrated　using　vibration　measurements　from　both　the　finite　element　model　of　a　highway　bridge　and　field　monitoring　data　from　an　actual　bridge.　The　results　show　that　the　proposed　method　successfully　synchronizes　vibration　signals　and　identifies　mode　shapes,　even　in　the　presence　of　modal　node　phenomena.　Copyright　©　2025　Tao　Chen　et　al.　Structural　Control　and　Health　Monitoring　published　by　John　Wiley　&　Sons　Ltd.