The tensile behavior of the thread-fixed one-side bolted T-stub to tube connection under fire and post-fire circumstances was studied. Fire tests were conducted using both transient-state and steady-state methods, and a comparison was made with standard high-strength bolted connections. The post-fire test analyzed the influence of temperature and applied load on the residual behavior of the connection. The results revealed four typical failure modes of the connection, all the four modes remained unchanged in both fire and post-fire scenarios. The connection exhibited a rapid decrease in tensile performance at high temperatures. No thread failure on the steel tube column wall occurred before yielding in the connection. In the post-fire test, the residual load-bearing capacity of the connections was basically the same as at room temperature, indicating that the connections still possess good load-bearing capacity after a fire. The performance of the one-side bolts in connections with end-plate yielding accompanied by bolt failure is similar to that of standard bolts. Based on the test results, a method for calculating the load-bearing capacity of one-side bolted connections at high temperatures was proposed, and the calculated results matched well with the test results.