Abstract Intraoperative surgery has created a need to develop new kinds of surgical tools. Also, the development of imaging techniques and devices has precipitated the need. Robotics plays an increasingly important role in surgery. A robot can yield better accuracy, smaller movements and, as a result, a faster healing process than a normal operation would require for recovering and healing larger cuts in the human body. Magnetic resonance imaging, MRI, is one of the safest imaging techniques, and it has excellent soft tissue contrast. In the last few years, MRI has become a more frequently-used technique in the intraoperative surgery, such as the biopsy. Brain biopsies in particular are easier to perform by the help of MRI. When designing a robot, or any other mechatronic device, for an MR environment, it becomes vital to consider its appropriateness, i.e., electric and magnetic compatibility with MRI. The latter is a notion related to the surgical procedure and the magnetic field being applied. It implies that instrumentation has to be more compatible with MR in higher magnetic fields. In this study, an MR-compatible robot was developed to work inside open MRI equipment. The MR compatibility of the robot was evaluated, using the testing method evolved during the study. The method helps select the suitable material and parts for mechatronic devices operating under MRI. Most notably, this work also devised and introduced new types of sensors to achieve better MR compatibility of the equipment. As a result of this research, a suitable material was developed for the robot's body as well as for the sensors, actuators and tools. Furthermore, it was deduced that some sensors and the control system when powered can not be used in the MR scanner at all. A further result was that the movement of a robotic arm does not disturb image quality in any way. The testing method developed in this research helps address the compatibility issues arising from the use of any device that works in MRI. The testing method can be used for magnetic fields of different strengths. The robot and the control parts constructed in the research were tested under a 0.23-T open MRI scanner. The results show which materials and fibre optics provide a highly MR compatible solution for an MRI environment. The results also show that normal electric motors can not be driven close to the magnetic field while imaging.