Objectives The cellular composition of body fluids (BF) provides insight into disease pathology and is an important diagnostic parameter. The well-established Sysmex XN haematology analyser (XN) offers automated BF analysis and is in routine use in many laboratories. In this study the performance of the new Sysmex XR analyser (XR) in testing BF is compared to the XN. Methods Cerebrospinal, pleural, peritoneal, and synovial fluids, as well as bronchoalveolar lavage (BAL) samples, were processed in BF mode on both analysers. Standard statistical methods were used to evaluate the performance of XR compared to the reference XN. Results Cell counts were generated from a total of 356 measurements from 307 patient BF samples. After application of exclusion criteria, 86 cerebrospinal, 77 peritoneal, 78 pleural, and 89 synovial fluid sample pairs were compared. An excellent correlation coefficient (r) between the two analysers was observed for all diagnostic parameters; WBC-BF: 0.996, RBC-BF: 0.974, TC-BF: 0.995, MN#: 0.994, MN%: 0.830, PMN#: 0.985 and PMN%: 0.835. The research parameters also performed equally well (r values of 0.900–0.994). The performance of diluted and undiluted samples was equally good. Similar results for diagnostic and research parameters were obtained from 62 BAL samples (r values of 0.899–0.992). Conclusions This study demonstrates that the automated BF counts on the new Sysmex XR analyser are equivalent to that of the XN for all BF types analysed.