A multi-fluid heat exchanger (10) is provided for transferring heat between a common fluid and a first fluid in one core section (22), and between the common fluid and a second fluid in another core section (28) of the heat exchanger (10). The core sections (22,28) are located in a series arrangement with respect to the flow of the common fluid through the heat exchanger (10) by folding the heat exchanger (10), with the core sections (22,28) being connected by folded portions (20) of the header pipes (12,14) that direct the first and second fluid flows to the interiors of the core sections (22,28).