Here we report muon spin rotation (𝜇⁢SR) experiments on the temperature and field dependence of the effective magnetic penetration depth 𝜆⁡(𝑇) in the 𝜂-carbide-type suboxide Ti₄⁢Ir₂⁢O, a superconductor with a considerably high upper critical field. The temperature dependence of 𝜆⁡(𝑇), obtained from transverse-field (TF)-𝜇⁢SR measurements, is in perfect agreement with an isotropic fully gaped superconducting state. Furthermore, our ZF 𝜇⁢SR results confirm that the time-reversal symmetry is preserved in the superconducting state. We find, however, a remarkably small ratio of 𝑇c/𝜆−20∼1.22. This value is close to most unconventional superconductors, showing that a very small superfluid density is present in the superconducting state of Ti₄⁢Ir₂⁢O. The presented results will pave the way for further theoretical and experimental investigations to obtain a microscopic understanding of the origin of such a high upper critical field in an isotropic single-gap superconducting system.