The Ti–(18−20)Nb–(1−1.2)Si alloys are obtained by electron-beam melting; the sizes of the ingots are as follow: $d$ = 60 mm, $l$ = 650 mm. As shown, the applied smelting method provides a more stable phase composition of $\alpha$ + $\beta$ + (Ti, Nb)$_{3}$Si in the cast alloys. Hot deformation is carried out at $T$ $\cong$ 1000°C by means of the rotary forging up to $d$ = 20 mm, followed by thermomechanical treatment (TMT‒screw rolling with water cooling) up to $d$ = 12 mm; quenching in water is carried out at 1050°С with a holding time of 30 min. The structure after deformation is non-equilibrium, consisting of the $\alpha$($\alpha^{'}$)-phase, the residual metastable $\beta$-phase, a small amount of large (Ti, Nb)$_{3}$Si silicides mainly on the boundaries of the primary $\beta$-grains, as well as dispersed silicides on structural defects, that causes the high strength $\sigma_{B}$ = 1155 MPa, but low plasticity $\delta$ = 3.5%. During the quenching of the deformed Ti–(18−20)Nb–(1−1.2)Si alloys at 1050°C, the orthorhombic $\alpha^{''}$-phase is formed, and the amount of silicides increases. Herewith, the strength is slightly reduced to $\sigma_{B}$ = 1135 MPa with significant increase in plasticity $\delta$ = 9%. Two-stage deformation including TMT with final quenching in water at 1050°C causes the release of a larger amount of dispersed silicides and, as a result, the formation of the $\alpha^{''}$-phase depleted with alloying elements and the residual $\beta$-phase. The resulting structure provides a better combination of mechanical properties ($\sigma_{B}$ = 1165 MPa, $\delta$ = 12.5%) due to dispersion strengthening with silicides and increased plasticity of the solid solution. For deformed experimental Ti–(18−20)Nb–(1−1.2)Si alloys, the quenching temperature $T$ = 1080 $\pm$ 10°C is also determined that allows obtaining the maximum strength $\sigma_{B}$ = 1190 MPa, while maintaining plasticity at the level of $\delta$ = 9.5%.