Adj A/Prof Koh Pei Lin graduated from the Medical Faculty of the National University of Singapore in 1999. She received the Loke-Cheng Kim Foundation scholarship for her undergraduate studies. Upon graduation, she was awarded the Lee Kuan Yew Gold Medal. She received her paediatrics post-graduate training in National University Hospital(NUH) and obtained her post-graduate degrees - Membership of the Royal College of Paediatrics and Child Health (UK) and Master of Medicine in Paediatrics (NUS, Singapore) in 2003. She was awarded the Prof Wong Hock Boon Gold Medal for the latter. She completed her advanced specialist training in general paediatrics in November 2006. She was awarded Fellowship of the Royal College of Paediatrics and Child Health (FRCPCH, UK) in 2018.

Adj A/Prof Koh has dual paediatric sub-speciality accreditation in Paediatric haematology-oncology and Paediatric Critical Care. She runs paediatric haematology clinics in the Viva-University Children's Cancer Centre located within NUH. She has a special interest in benign blood disorders such as thalassaemia, bleeding disorders such as haemophilia and immune (idiopathic) thrombocytopenia (ITP) and thrombosis. She leads the paediatric haemophilia treatment centre (HTC) in NUH.

She was the head of Paediatric Intensive Care Unit (PICU) from December 2009 till March 2017, and is currently a senior consultant in PICU. Her research interests include haematological issues in PICU, end-of-life issues in the PICU and new therapies for haemophilia. 

She currently volunteers with the Hospice Care Association (HCA) and Starpals (paediatric home palliative care service). Adj A/Prof Koh loves nature and the great outdoors. In her free time, she engages in scuba diving and trekking trips.