The exploiting of novel Er3+/Yb3+ co-doped material with broad wavelength tunability in 1.5–1.6 μm is necessary for meeting the application requirements in broadband tunable laser and optical amplifier as well as femtosecond ultrashort pulse laser. End-pumped by a continuous-wave 976.5 nm laser diode, the wavelength tunability of an Er:Yb:Ca3NbGa3Si2O14 crystal with a broad and flat gain band in 1.5–1.6 μm was investigated. At an absorbed pump power of 7.4 W and a pump beam waist diameter of 200 μm, a continuously tunable 1.5–1.6 μm laser with a range of 83 nm was realized in the crystal. When the pump beam waist diameter was decreased to 100 μm, the wavelength tuning range of the laser increased to 102 nm. The obtained maximum continuous-wave output power was higher than 100 mW.