This work investigates the Fermi surface of the Ti-doped ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$ superconductor under pressures up to 2.1 GPa. Upon the application of both chemical and physical pressure in ${\mathrm{CsTi}}_{0.1}{\mathrm{V}}_{2.9}{\mathrm{Sb}}_5$, the superconducting transition temperature increases to $T_c=6.5$ K, nearly three times higher than that of the parent compound. To probe the Fermi surface under pressure, in situ magnetoresistance (MR) measurements are performed in magnetic fields up to 18 T at four pressure points: 0.25, 0.47, 1.55, and 2.1 GPa. The MR data at 0.25 GPa reveal clear Shubnikov–de Haas oscillations with frequency components at $F_{\alpha }=21$ T, $F_{\beta }=83$ T, $F_{\gamma }=709$ T, and $F_{\delta }=804$ T. These quantum oscillation frequencies, which correspond to extremal cross-sectional areas of the Fermi surface, vanish above 0.47 GPa, strongly indicating a pressure-induced Fermi surface reconstruction. To interpret these results, we conduct density functional theory calculations of the electronic band structure and Fermi surface. The calculations show a shift in Dirac points and Van Hove singularities near the Fermi level, along with notable changes in the Fermi surface topology as Ti doping increases, confirming that Ti substitution effectively tunes the electronic structure of ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$. Our combined experimental and theoretical study offers valuable insight into how both chemical and physical pressure can be used to engineer the electronic structure of ${\mathrm{CsTi}}_{0.1}{\mathrm{V}}_{2.9}{\mathrm{Sb}}_5$, providing a pathway for tuning correlated phenomena in kagome superconductors.

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• Charge density waves
• Electronic structure
• Fermi surface
• Superconducting phase transition