Nine new monoterpenoid indole alkaloids, uncarialins A-I (<b>1</b>-<b>9</b>), were isolated from <i>Uncaria rhynchophylla</i> as well as 14 known analogues (<b>10</b>-<b>23</b>). Their structures were determined by HRESIMS, 1D and 2D NMR, and experimental and calculated electronic circular dichroism data. Compounds <b>5</b>, <b>7</b>, <b>15</b>, and <b>22</b> displayed significant agonistic effects against the 5-HT<sub>1A</sub> receptor with EC<sub>50</sub> values of 2.2 ± 0.1, 0.1 ± 0.1, 1.6 ± 0.3, and 2.0 ± 0.5 μM, respectively. The mechanisms of action of these four compounds with the 5-HT<sub>1A</sub> receptor were investigated by molecular docking, and the results suggested that amino acid residues Asp116, Thr196, Asn386, and Tyr390 played critical roles in the observed activity of the above-mentioned compounds.