We experimentally demonstrate an ultrafast mode-locker based on a ${\mathrm{CoSb}}_3$ skutterudite topological insulator for femtosecond mode-locking of a fiber laser. The mode-locker was implemented on a side-polished fiber platform by depositing a ${\mathrm{CoSb}}_3/\mathrm{PVA}$ composite. The measured modulation depth and saturation power for the transverse-electric mode input were $～5\%$ and $～8.7\mathrm{W}$, respectively, and $～2.8\%$ and $～10.6\mathrm{W}$ for the transverse-magnetic mode input. By incorporating this mode-locker into an erbium-doped fiber-based ring cavity, we were able to readily generate mode-locked, soliton pulses having a pulse width of $～833\mathrm{fs}$ at 1557.9 nm. The 3-dB bandwidth of the output pulses and time-bandwidth product were $～3.44$ and 0.353 nm, respectively. To the best of the authors’ knowledge, this is the first demonstration of the use of a skutterudite-based saturable absorber for femtosecond mode-locked pulse generation.