Introduction: This research aims to develop a 3D-printed ergonomic handle design for a steerable laparoscopic instrument with minimised part assembly. Steerable laparoscopic instruments are used in minimally invasive surgery (MIS). MIS is a technique where surgeons insert long slender surgical instruments through small incisions of five to ten millimetres in the abdominal wall. According to various studies regarding the ergonomics of laparoscopic instruments, improvements in the control and handle design are necessary. Non-ergonomic design and control, combined with extensive surgery, can cause physical discomfort, muscle fatigue, mental stress, and other complications to the surgeon that can adversely affect the patient. Improvements in the design can overcome inconvenient and uncomfortable movements of laparoscopic instruments to make MIS safer for surgeons and patients. In addition to the improvements in ergonomics, a reduction in assembled parts in current laparoscopic instruments can shorten the assembly time, resulting in lower manufacturing costs. 3D-printing offers design freedom to enable complex structures with minimised part assembly and has the potential to customise the instrument specifically to the surgeon. Methods: The working principles and ergonomics of sixteen steerable laparoscopic instruments were analysed. Requirements were set up from the analysed laparoscopic instruments, handle design ergonomics and control ergonomics to develop an ergonomic handle design. Concepts have emerged from the requirements, and the most promising concept has been developed towards a final design. From the final proposed handle design emerged a working prototype, The LapaJoy. The 3D-printing technique of stereolithography was used to manufacture the LapaJoy. Steering, grasping, bending and locking tests were conducted to compare the retrieved data with the requirements to validate and evaluate the working principle and performance of the LapaJoy. Results: The LapaJoy consists of five assembled parts and allows the surgeon to control the four different functions of the instrument. The surgeon can control the end-effector in two degrees of freedom, lock the end-effector's position, open and close the grasping forceps, and lock the grasping forceps in place. All four functions of the LapaJoy can be performed by a novel two-finger control system using the index finger and thumb. The results show that the LapaJoy can manipulate the end-effector in two degrees of freedom by 20 degrees and lock the end-effector in any desired position. The instrument's grasper is functional, and the grasping forceps can be locked in place upon release of the grasper trigger. However, an analysation showed a reduction in the opening range of the grasping forceps with each opening and closing cycle. Furthermore, a material response wherein deformation of the steering segment's flexure occurred. The steering segment's flexure was deformed by 9.9 degrees after applying almost 1 N to the grasping forceps in the vertical direction. In addition, fatigue and failure of the grasper and joystick design occurred during extensive use and testing. Conclusion: By developing the 3D-printed ergonomic handle design with minimised part assembly, new knowledge was acquired in the possibilities of 3D-printing as a manufacturing technique for laparoscopic instruments. Future research is recommended to increase the steering angle and use more durable materials to create a more reliable product. The instrument's performance showed excellent potential in 3D printable laparoscopic instruments with minimised part assembly. The LapaJoy has the prospect of being an ergonomic, low cost, disposable MIS instrument.