<b><i>Aim:</i></b> To evaluate the agreement between intra-ocular pressure (IOP) measurements with the Diaton and the Goldmann applanation tonometers (GAT). <b><i>Methods:</i></b> In this cross-sectional observational study, a total of 196 eyes of 196 participants (66 patients with glaucoma, 130 healthy subjects) were included. IOP measurements were obtained from all patients using the Diaton and GAT. <b><i>Results:</i></b> The average age of the patients enrolled in this study was 48.3 ± 14.6 years (range 18–79). The overall mean IOP measured by the Diaton was 17.2 ± 6.4 mm Hg, while that in glaucoma patients was 17.9 ± 6.2 mm Hg and in the control group 15.8 ± 4.9 mm Hg. Pearson’s correlation coefficient showed a moderate correlation in IOP measurements by the two instruments in healthy controls (r = 0.460, p < 0.01); however, the same correlation for the glaucomatous subjects was noted to be poor (r = 0.261, p = 0.57). The limits of agreement (95% confidence intervals) ranged from –9.9 to +11.2 and from –15.3 to +19.7 mm Hg in healthy controls and glaucoma patients, respectively. <b><i>Conclusion:</i></b> The Diaton measurements do not correlate well with those provided by applanation tonometry. The two tonometers show very wide limits of agreement so they may not be used interchangeably in clinical practice for the measurement of IOP.