Magnetic (χ), transport (ρ) and heat capacity (Cm) properties of CeIrSi are investigated to elucidate the effect of geometric frustration in this compound with trillium type structure because, notwithstanding its robust effective moment, µ eff ≈ 2.46µB, this Ce-lattice compound does not undergo a magnetic transition. In spite of that it shows broad Cm(T )/T and χ(T ) maxima centered at Tmax ≈ 1.5 K, while a ρ ∝ T 2 thermal dependence, characteristic of electronic spin coherent fluctuations, is observed below T coh ≈ 2.5 K. Magnetic field does not affect significantly the position of the mentioned maxima up to ≈ 1 T, though χ(T ) shows an incipient structure that completely vanishes at µ0H ≈ 1 T. Concerning the ρ ∝ T 2 dependence, it is practically not affected by magnetic field up to µ0H = 9 T, with the residual resistivity ρ0(H) slightly decreasing and T coh (H) increasing. These results are compared with the physical properties observed in other frustrated intermetallic compounds.