Hyperfine structure and isotope shifts have been measured for the ground and isomeric states in the neutron deficient isotopes 179–184Tl using the 276.9-nm transition. The experiment has been performed at the CERN Isotope Separator On-Line facility using the in-source resonance-ionization laser spectroscopy technique. Spins for the ground states in 179,181,183Tl have been determined as I = 1/2. Magnetic moments and changes in the nuclear mean-square charge radii have been deduced. By applying the additivity relation for magnetic moments of the odd-odd Tl nuclei the leading configuration assignments were confirmed. A deviation of magnetic moments for isomeric states in 182,184Tl from the trend of the heavier Tl nuclei is observed. The charge radii of the ground states of the isotopes 179–184Tl follow the trend for isotonic (spherical) lead nuclei. The noticeable difference in charge radii for ground and isomeric states of 183,184Tl has been observed, suggesting a larger deformation for the intruder-based 9/2− and 10− states compared to the ground states. An unexpected growth of the isomer shift for 183Tl has been found.