Bus Paris to Amsterdam

Traveling by bus from Paris to Amsterdam has become easier over the last few years with the introduction of Megabus and iDBUS in addition to Eurolines. Each coachline now operate regular services from Paris to Amsterdam and return. Notice that bus stations are normally outside of the city center so it pays to check closely where they stop before planning your departure and arrival transport.

Eurolines

One of the bus services you can use to get from Paris to Amsterdam is the Eurolines bus. Tickets for the Eurolines bus can be purchased online using a credit card. Adult fares costs between 25 to 50 EUR one-way from Paris to Amsterdam. The Eurolines coach to Amsterdam is not much cheaper than taking a high-speed train from Paris to Amsterdam. The bus journey on the Eurolines Paris Amsterdam service takes about 7 hours. It will take you from Paris Gallieni Porte Bagnolet to Amsterdam Amstel train station. The metro station "Porte de Bagnolet" is at the end of line 3. It is in the northeast of Paris, about 30 to 40 minutes from the Cite, Paris metro station.
www.eurolines.fr

iDBus

This is a bus service operated by French company SNCF which started in 2012. This company offers comfortable coach travel between Paris and Amsterdam. There are only 48 seats per coach, there is Wifi and electrical sockets on board, the seats are adjustable and the departure and arrival stations are close to the city. The prices starting from 39 EUR for an adult fare. The travel time is about 6 hours and 50 minutes from Paris Bercy to Amsterdam Sloterdijk Station. Paris Bercy station is two stops from Chatelet station on line 14, the fastest metro line in Paris. Amsterdam Sloterdijk Station is in the northwest of the city center, it is well connected by metro and tram lines. 
www.idbus.com

Megabus

This is a service operated by Stagecoach a UK based company. There are two services traveling from Paris to Amsterdam everyday which take about 8 hours. The prices start from as low as 12 GBP one-way. They depart from Porte Maillot Coach park and arrive at Amsterdam, Zeeburg P&R coach park at Zuiderzeeweg. Both stops are outside the city center so really plan in advance to get there.
www.megabus.com