Due　to　the　rapid　reaction　kinetics,　the　morphology　of　chitosan/tripolyphosphate　nanoparticles　was　difficult　to　control.　We　mixed　chitosan　and　tripolyphosphate　through　a　multi-inlet　vortex　mixer　at　different　mixing　efficiency　and　characteristic　mixing　time　(τmix).　Below　a　critical　τmix,　the　aggregation　of　primary　chitosan/TPP　particles　can　be　ceased.　The　corresponding　aggregation　time　of　primary　particles　(τagg)　was　dependent　on　the　ionic　strength,　the　degree　of　deacetylation　and　molecular　weight　of　chitosan.　Moreover,　the　particle　compactness　was　estimated　from　the　hydrodynamic　diameter　and　the　turbidity　using　a　model　based　on　the　Mie　theory.　Slow　and　nonhomogeneous　mixing　led　to　more　compact　nanoparticles,　while　rapid　and　homogeneous　mixing　produced　nanoparticles　with　a　higher　swelling　ratio.　Besides,　the　ionic　strength　and　polymer　concentration　could　affect　the　internal　structure　of　nanoparticles.　This　study　revealed　the　significance　of　mixing　on　the　internal　structure　of　chitosan/TPP　nanoparticles,　which　could　guide　the　preparation　of　other　ionically-crosslinked　polysaccharide　colloids.　©　2022　Elsevier　Ltd