Phosphorene nanotubes (PNTs), one-dimensional counterparts of monolayer black phosphorus, exhibit chirality-dependent physical properties due to the inherent anisotropy of the phosphorene lattice. In this work, we perform molecular dynamics simulations to systematically investigate the thermal stability and mechanical behavior of armchair (0,44) and zigzag (60,0) PNTs with comparable diameters (~6.4 nm) under both tensile and compressive loadings across a temperature range of 50–300 K. Thermal stability analysis reveals that both PNTs remain stable above room temperature, with critical stability thresholds of 390 K for armchair and 320 K for zigzag PNTs, indicating superior thermal resilience of the armchair configuration. Mechanical characterization demonstrates pronounced anisotropy in both tensile and compressive moduli. At 300 K, the tensile moduli are 90.36 GPa (armchair) and 20.14 GPa (zigzag), while the compressive moduli are 98.40 GPa (armchair) and 20.43 GPa (zigzag). These values closely mirror the elastic behavior of monolayer phosphorene along corresponding crystallographic orientations. A strong thermal softening effect degrades tensile performance: as temperature rises from 50 K to 300 K, the fracture strength decreases by approximately 50% for both chiralities, accompanied by a 55–60% reduction in fracture strain. At 300 K, the armchair PNT exhibits higher fracture strength (3.43 GPa) but lower fracture strain (0.046) compared to the zigzag PNT (1.69 GPa and 0.093). Under compression, the temperature dependence is relatively weak overall. However, a striking chirality-specific failure mechanism emerges near the thermal stability limit. At 300 K, armchair PNTs fail via buckling-dominated structural instability, whereas zigzag PNTs undergo crushing-dominated material failure where thermally weakened P–P bonds rupture before buckling occurs. At room temperature, the buckling strengths are 2.32 GPa (armchair) and 2.13 GPa (zigzag), with corresponding buckling strains of 0.023 and 0.096, indicating superior compressibility of zigzag PNTs despite slightly lower strength. Compared to monolayer phosphorene, the curvature-induced prestrain from rolling into nanotubes weakens the axial tensile capacity—both tensile strength and fracture strain are reduced. Under compression, the critical buckling strain also decreases after rolling. However, the buckling strength increases for both chiralities as a result of the 'reinforcing effect' of the tubular geometry's circumferential constraint.