An infusion fluid warmer comprising: - a casing shell having an upper wall structure and a lower, opposing, wall structure; said casing shell enclosing: - a fluid channel or passage extending through the casing shell in-between the upper and lower wall structures, - fluid inlet and outlet ports coupled to opposite ends of the fluid channel or passage to allow a flow of infusion fluid through the casing shell, - a housing shell formed in a thermally conducting and electrically insulating material and comprising a plate shaped upper wall structure and an opposing separate lower plate shaped wall structure, - a first heating element (406a, 406b) bonded to the plate shaped upper wall structure and thermally coupled thereto, a second heating element (406d, 406c) bonded to the plate shaped lower wall structure and thermally coupled thereto; and - an aluminium heat exchanger sandwiched in-between the plate shaped upper wall structure and the opposing lower plate shaped wall structure and thermally coupled thereto, wherein the first heating element (406a, 406b) is bonded to a surface of the plate shaped upper wall structure facing away from the fluid channel and the second heating element (406d, 406c) is bonded to a surface of the plate shaped lower wall structure facing away from the fluid channel, characterized in that the fluid channel or passage extends through the aluminium heat exchanger between a fluid inlet port and a fluid outlet port of the aluminium heat exchanger and is substantially straight with a rectangular cross-sectional profile such that heat energy is transferred to the infusion fluid by direct physical contact with heat exchanger material. - a casing shell having an upper wall structure and a lower, opposing, wall structure; said casing shell enclosing: - a fluid channel or passage extending through the casing shell in-between the upper and lower wall structures, - fluid inlet and outlet ports coupled to opposite ends of the fluid channel or passage to allow a flow of infusion fluid through the casing shell, - a housing shell formed in a thermally conducting and electrically insulating material and comprising a plate shaped upper wall structure and an opposing separate lower plate shaped wall structure, - a first heating element (406a, 406b) bonded to the plate shaped upper wall structure and thermally coupled thereto, a second heating element (406d, 406c) bonded to the plate shaped lower wall structure and thermally coupled thereto; and - an aluminium heat exchanger sandwiched in-between the plate shaped upper wall structure and the opposing lower plate shaped wall structure and thermally coupled thereto, wherein the first heating element (406a, 406b) is bonded to a surface of the plate shaped upper wall structure facing away from the fluid channel and the second heating element (406d, 406c) is bonded to a surface of the plate shaped lower wall structure facing away from the fluid channel, characterized in that the fluid channel or passage extends through the aluminium heat exchanger between a fluid inlet port and a fluid outlet port of the aluminium heat exchanger and is substantially straight with a rectangular cross-sectional profile such that heat energy is transferred to the infusion fluid by direct physical contact with heat exchanger material.