Background In Kenya, it is estimated that there are approximately 3.6 million children aged <18 years who have been orphaned or who are vulnerable. We examined the data from the second Kenya AIDS Indicator Survey (KAIS 2012) to determine the number and profile of orphans and vulnerable children (OVC) in Kenya who were aged <18 years. Methods KAIS 2012 was a nationally representative, population-based household survey. We analyzed the data for all the children from birth to age 17 years who resided in an eligible household so as to determine whether their parents were alive or had been very ill to define their OVC status. Results We estimated that there were 2.6 million OVC in Kenya in 2012, of whom 1.8 million were orphans and 750,000 were vulnerable. Among orphans, 15% were double orphans. Over one-third of all the OVC were aged between 10 and 14 years. Households with ≥1 OVC (12% of all households) were usually in the lowest 2 wealth quintiles, and 22% of OVC households had experienced moderate or severe hunger. Receipt of OVC support services was low for medical (3.7%), psychological (4.1%), social (1.3%), and material support (6.2%); educational support was slightly more common (11.5%). Orphanhood among children aged <15 years increased from 1993 to 2003 (P < 0.01) but declined from 2003 to 2012 (P < 0.01). Conclusions The 2.6 million OVC constitute a significant proportion of Kenya’s population aged <18 years. Special attention should be paid to OVC to prevent further vulnerability and ensure their well-being and development as they transition into adulthood.