Background:　Cycling　is　known　to　be　beneficial　for　human　health.　Studies　have　suggested　significant　associations　of　physical　activity　with　macroscale　built　environments　and　streetscapes.　However,　whether　good　streetscapes　can　amplify　the　benefits　of　a　favorable　built　environment　on　physical　activity　remains　unknown.　Objective:　This　study　examines　whether　streetscape　perceptions　can　modify　the　associations　between　accessibility,　land　use　mix,　and　bike-sharing　use.　Methods:　This　cross-sectional　study　used　data　from　18,019,266　bike-sharing　orders　during　weekends　in　Shanghai,　China.　A　500　x　500　m　grid　was　selected　as　the　analysis　unit　to　allocate　data.　Bike-sharing　use　was　defined　as　the　number　of　bike-sharing　origins.　Street　view　images　and　a　human-machine　adversarial　scoring　framework　were　combined　to　evaluate　lively,　safety,　and　wealthy　perceptions.　Negative　binomial　regression　was　developed　to　examine　the　independent　effects　of　the　three　perceptual　factors　in　both　the　univariate　model　and　fully　adjusted　model,　controlling　for　population　density,　average　building　height,　distance　to　nearest　transit,　number　of　bus　stations,　number　of　points　of　interest,　distance　to　the　nearest　park,　and　distance　to　the　central　business　district.　The　moderation　effect　was　then　investigated　through　the　interaction　term　between　streetscape　perception　and　accessibility　and　land　use　mix,　based　on　the　fully　adjusted　model.　We　also　tested　whether　the　findings　of　streetscape　moderation　effects　are　robust　when　examinations　are　performed　at　different　geographic　scales,　using　a　small-sample　statistics　approach　and　different　operationalizations　of　land　use　mix　and　accessibility.　Results:　High　levels　of　lively,　safety,　and　wealthy　perceptions　were　correlated　with　more　bike-sharing　activities.　There　were　negative　effects　for　the　interactions　between　the　land　use　Herfindahl-Hirschman　index　with　the　lively　perception　(beta=-0.63;P=.01)　and　safety　perception　(beta=-0.52;　P=.001).　The　interaction　between　the　lively　perception　and　road　intersection　density　was　positively　associated　with　the　number　of　bike-sharing　uses　(beta=0.43;　P=.08).　Among　these,　the　lively　perception　showed　the　greatest　independent　effect　(beta=1.29;　P＜.001),　followed　by　the　safety　perception　(beta=1.22;　P=.001)　and　wealthy　perception(beta=0.72;　P=.001).　The　findings　were　robust　in　the　three　sensitivity　analyses.　Conclusions:　A　safer　and　livelier　streetscape　can　enhance　the　benefits　of　land　use　mix　in　promoting　bike-sharing　use,　with　a　safer　streetscape　also　intensifying　the　effect　of　accessibility.　Interventions　focused　on　streetscape　perceptions　can　encourage　cycling　behavior　and　enhance　the　benefits　of　accessibility　and　land　use　mix.　This　study　also　contributes　to　the　literature　on　potential　moderators　of　built　environment　healthy　behavior　associations　from　the　perspective　of　microscale　environmental　perceptions.