Can I use my German Transit Visa to transit in Netherlands?

Absent added information on your visa, other visas you may have, and on your flight plans, here's the German Missions in Nigeria explanation of the Category A (Airport transit visa), as well as the German Missions in the United States document, with an expanded description, dated April 2017.

It states that nationals of certain countries, including Nigeria, are required to be in possession of an airport transit visa when passing through the international transit area of airports in Germany.

There are exceptions: Nigerian citizens do not need an airport transit visa if they are in possession of a valid visa

• for a Schengen Member State
• for state party to the Agreement on the European Economic Area of 2 May 1992
• for Japan, Canada, Switzerland or the United States of America
• or, if after using one of these visas, they are returning to Nigeria from any of these countries.

Please note that an airport transit visa only allows a short stay in the international transit area of some airports:

• Frankfurt/Main (open 24 hours)
• Munich (open 24 hours)
• Hamburg (4:30 a.m. - 11:30 p.m. only)
• Düsseldorf (6:00 a.m. - 9:00 p.m. only) and if the airline has arranged the transit beforehand with the authorities responsible for cross-border security (the Federal Police)
• Cologne/Bonn (4:30 a.m. - 11:00 p.m. only)
• Berlin (06:00 a.m. - 11:00 p.m. only) at Berlin-Tegel, for Air Berlin passengers only. The airline has to arrange the transit beforehand with the authorities responsible for cross-border security (the Federal Police). The connection time must be at least 75 minutes.

Airport transit privilege does not apply and you will need a visitor visa if

1. you have to pick up your baggage and/or have to check-in again (please verify with your airline) or
2. you are transiting through two or more airports in the Schengen Countries (for example: Miami-Frankfurt-Paris-India or New York-Frankfurt-Munich-India) or
3. you hold an open ticket.

According to the Schengen Visa Code, transit visas are usually valid for all international airports within the Schengen area:

1. An airport transit visa shall be valid for transiting through the international transit areas of the airports situated on the territory of Member States.

However there is an exemption to that rule...

5. If the applicant is required to hold an airport transit visa in accordance with the provisions of Article 3(2), the airport transit visa shall be valid only for transiting through the international transit areas of the airports situated on the territory of the Member State(s) concerned

And Article 3(2) states the following:

2. In urgent cases of mass influx of illegal immigrants, individual Member States may require nationals of third countries other than those referred to in paragraph 1 to hold an airport transit visa when passing through the international transit areas of airports situated on their territory. Member States shall notify the Commission of such decisions before their entry into force and of withdrawals of such an airport transit visa requirement.

Which means that if citizens of your country are required to hold an airport transit visa by a specific Schengen state, then that particular visa is only valid within the international airports of that state. However if your nationality is required to hold a transit visa for the entire Schengen area, then that visa would be valid for all Member States.

In your particular scenario Nigeria is on the common airport transit visa list, so your visa is also valid for the Netherlands. So the answer is yes, you may use your existing visa to transit.