Alpha (α)-thalassaemia is a common genetic disorder worldwide caused by the deletion and rarely non-deletional mutations of the α-globin gene. Nearly 70 types of non-deletional mutations have been reported worldwide, and this review focuses on the common ones affecting α-thalassaemia patients. The common mutations are initiation codon mutation, codon 30, haemoglobin (Hb) Constant Spring, Hb Quang Sze, Hb Adana and Hb Evora. The haematological parameters of non-deletional mutations usually show mild changes. However, a severe reduction in haemoglobin level, mean corpuscular haemoglobin (MCH), mean corpuscular volume (MCV), and mean corpuscular haemoglobin count (MCHC) has been observed among compound heterozygous HbH disease, involving both deletional and non-deletional mutations. Although non-deletional mutations are rarely reported, it requires the study of more cases to understand the clinical phenotypes that lead to severe clinical manifestations.