Nigeria’s 1999 Constitution doesn’t treat all citizens the same way on this question — and the distinction it draws is the one most guides skip.
Section 28 of the 1999 Constitution is widely interpreted as permitting Nigerians who are citizens by birth to hold another citizenship without losing their Nigerian one — Nigeria doesn’t require them to renounce it. In practice, a Nigerian-by-birth naturalising in Germany today can generally keep both.
The same constitutional framework is generally read as more restrictive for citizens who acquired Nigerian citizenship through registration or naturalisation rather than birth — the dual-citizenship allowance is specifically tied to being a citizen by birth. This distinction matters enormously and is the detail most informal guidance misses entirely.
If your Nigerian citizenship came through your parents or birth on Nigerian soil, the dual-citizenship allowance should apply to you. If you naturalised INTO Nigerian citizenship from somewhere else, don’t assume the same protection — confirm with the Nigerian High Commission before naturalising abroad.