Mr Geingob polled 56.3% in Wednesday’s election, well ahead of his nearest rival Panduleni Itula with 29.4%.
However, Mr Geingob’s tally was well down from the 87% with which he won his first term in 2014.
He went on social media to thank Namibians for returning him to office, promising to bring tangible improvements to their lives.
His Swapo party has ruled Namibia for nearly three decades since it gained independence from South Africa.
The sparsely-populated country has suffered from economic recession, hit by serious drought and low prices for its main mineral exports, diamonds and uranium.
The Bank of Namibia is predicting a third year of recession, with the economy due to shrink by 1.7% in 2019.