The electromagnetic wave (EMW) absorption properties in Heusler-type ferromagnetic Ni2+x Mn1-x Ga alloys were systematically investigated. Significant electromagnetic absorption performance at 2.0-18.0 GHz was observed for Ni2+x Mn1-x Ga alloys. The values of the complex permittivity (epsilon (r) ) and permeability (mu (r) ), as well as the reflection loss (RL), peak frequency (f (m)) and bandwidth (Delta f) of Ni2+x Mn1-x Ga can be effectively tuned by the alloy component (Ni/Mn ratio). The magnetic loss factor (tan delta (mu) ) shows pronounced multi-resonance behavior, and dielectric loss factor (tan delta (epsilon) ) has dramatic dielectric relaxation. The RL exceeding - 10 dB corresponding to 90% absorption of incident microwave can be achieved for the Ni2MnGa in a broad frequency range of 6.3-18.0 GHz together with the thickness from 1.66 to 4.75 mm. Particularly, the maximum RL reaches - 49.1 dB at 13.3 GHz with the thickness of 2.57 mm for Ni2MnGa. The present results indicated that the ferromagnetic Ni2+x Mn1-x Ga alloys could be attractive candidates for broadband and high-frequency EMW absorption.