Herein,　MoS2　nanoslices　were　simply　prepared　by　using　ultrasonic　treatment,　and　were　further　decorated　with　Au　nanoparticles　(AuNPs)　through　an　electrodeposition　process　to　obtain　the　MoS2/Au　nanocomposites.　The　obtained　nanocomposites　display　synergetic　electrocatalytic　effect　for　the　oxidation　of　dopamine　due　to　the　large　surface　area　and　two-dimensional　structure　of　the　MoS2　nanoslices,　combining　with　the　high　catalytic　activity　and　good　conductivity　of　AuNPs.　An　electrochemical　sensor　was　constructed　based　on　MoS2/Au-modified　carbon　paste　electrode,　for　sensitive　and　quantitative　determination　of　dopamine.　The　prepared　electrochemical　sensor　proves　excellent　analytical　performances:　very　high　sensitivity,　wide　linear　ranges　(0.5–300　μM),　and　low　detection　limit　(76　nM).　Moreover,　the　dopamine　sensor　also　displays　high　selectivity,　good　reproducibility　and　stability,　and　can　be　used　in　real　sample　analysis.　The　method　of　fabricating　high-efficiency　electrocatalysts　and　electrochemical　sensors　proposed　in　this　study　provides　a　good　reference　for　developing　more　functionalized　nanocomposites　and　for　extending　practical　applications.　©　2019　by　the　authors.　Licensee　MDPI,　Basel,　Switzerland.