Save the Children says the number could be higher due to this year's health workers' strike.
It claimed the lives of 22,473 people in 2015 - the last year for recorded figures - almost all under the age of two.
In Kenya, one of the most badly affected regions is Turkana County.
More than 22,000 children a year are dying in Kenya due to failure to vaccinate against pneumonia, an international charity has said.
Save The Children's officials say they fear the statistics could have worsened considerably in 2017 as a result of the recent doctors' and nurses' strike.
According to a report by the UK-based charity, Kenya is one of the worst-affected countries by the respiratory disease in sub-Saharan Africa.
It claimed the lives of 22,473 people in 2015 - the last year for recorded figures - almost all under the age of two.
Pneumonia kills two children under the age of five globally every minute, or almost 1 million a year, which is more than malaria, diarrhoea and measles combined.
However, Save the Children says pneumonia can be easily treated with antibiotics such as amoxicillin.
The report, Fighting for Breath, shows that the children of the poorest in Kenya are most affected by pneumonia either due to distance from medical facilities or problems getting good treatment.
“Reaching a health facility is no guarantee of effective treatment,” the report says.
“Inaccurate diagnosis, shortages of frontline antibiotics, and weak referral systems combine to claim lives that could be saved,” it adds.
Surveys of essential medicine availability show that fewer than 60 per cent of facilities in Tanzania, Kenya, the Democratic Republic of Congo and Mauritania have Amoxicillin DT available, the most effective frontline treatment.
One potentially fatal consequence of pneumonia is hypoxaemia, a condition that leaves children with insufficient oxygen in their blood.
Some 2 million children are admitted to hospital each year with the condition and are left, quite literally, gasping for air.
The report says that pneumonia today is “overwhelmingly a disease of poverty, as it has been throughout history.”
The risks of contracting the disease are heavily skewed towards the poorest children, while the prospects for receiving accurate diagnosis, effective treatment and appropriate care are skewed towards those who are better off.
Unvaccinated children
Save the Children says that there nearly 27 million unvaccinated children in sub Saharan Africa, the highest figure world-wide apart from Asia.
The charity is calling for cheaper vaccines as well as coordinated action plans by governments to ensure universal access to healthcare.
It points out that the international community had made a commitment to end preventable child deaths by 2030.
“Decisions taken over the next few years on pneumonia will determine whether or not that pledge is honoured or broken,” the report says.
Worst affected
In Kenya, one of the most badly affected regions is Turkana County, where the acute respiratory disease is common among pastoralists who use charcoal and wood fuel for cooking.
Here, most children are offered vaccinations for pneumonia. However, a severe drought affecting the Horn of Africa region led to widespread hunger and malnutrition, which weakens the immune systems of the vulnerable including babies.
The nutrition situation in parts of Turkana remains classified as “extremely critical” and in total, 3.4 million people are expected to be in need of emergency food aid by the end of 2017.
Doctors who spoke to The Guardian newspaper estimate deaths from pneumonia to have doubled since the health workers' strike began in June.
