Objectives: To define characteristics of Klebsiella pneumoniae isolated from carriage and infections in mothers and their neonates belonging to a paediatric cohort in Madagascar. Methods: A total of 2000 mothers and their 2001 neonates were included. For each mother, vaginal and stool samples were collected at the birth. Additionally, upon suspicion of infection, samples were collected from suspected infected body sites in 121 neonates. Genomic sequences of all isolated K. pneumoniae were used for phylogenetic analyses and to investigate the genomic content of antimicrobial resistance genes, virulence genes and plasmid replicon types. Results: Five percent (n = 101) of mothers were K. pneumoniae positive. Of 251 collected K. pneumoniae isolates, 102 (40.6%) were from mothers and 149 (59.3%) were from neonates. A total of 49 (19.5%; all from infants except 1) isolates were from infected body sites. MLST identified 108 different STs distributed over the six K. pneumoniae phylogroups Kp1 to Kp6. We found 65 (25.8%) ESBL producers and a total of 101 (40.2%) MDR isolates. The most common ESBL gene was blaCTX-M-15 (in 99.3% of isolates expressing ESBL). One isolate co-harboured blaCTX-M-15 and blaNDM-1 genes. Three isolates from infected body sites belonged to hypervirulent-associated ST23 (n = 1) and ST25 (n = 2). We observed two cases of mother-to-child transmission and sustained K. pneumoniae carriage was identified in 10 neonates, with identical isolates observed longitudinally over the course of 18 to 115 days. Conclusions: This study revealed substantial genetic diversity and a high rate of antimicrobial resistance among K. pneumoniae isolated from both carriage and infections in Madagascar.