Grouted sleeve connections are widely used in precast concrete structures for joining rebar. In order to understand the behavior of grouted sleeves under and after fire, tensile tests are carried out on grouted sleeves with threaded bars under three different thermo-mechanical loading conditions, i.e., loading when temperature is constant, heating when a constant mechanical load is maintained and loading at room temperature on previously heated sleeves. Tensile tests of continuous rebar are also conducted for comparisons. Failure modes and degradation of mechanical properties of both grouted sleeve connections and continuous rebar subjected to above conditions are studied. It is found that the temperature resistances of the grouted sleeve connections with or without considering heating process are significantly different, while such differences are negligible for continuous rebar. It is also found that grouted sleeve connections can restore some of the mechanical capacities after they are cooled down to the room temperature. Finally, predictive models are proposed for potential adoption in fire resistance design and post fire evaluation of grouted sleeve connections.