The evidence that the Last Supper was a Seder includes that it was held within a day of when the Seder was scheduled. Although some would say that this is evidence that it was not a Seder, others point out that it was held early because Jesus and the disciples knew that the correct night would be too late, as Jesus was to be killed in Jerusalem the next day and that he had been betrayed by Judas. Jesus was quoted in Luke as saying that he earnestly desired to eat the “Passover meal” with his disciples before he suffered. Gospel records support the theory that the Last Supper was a Seder. Finally, there were similar features during both meals such as reclining during the meal and some of the foods that were eaten.
The evidence that the Last Supper was not a Seder includes that it may not have been held on the correct date for a Seder, but one day early. Luke used the word “apostles” instead of “the twelve” or “the disciples” which implied that the meal was important to the church. Only Jesus and the disciples were present, whereas during a Seder, typically it was a family event with men and women. The disciples argued over who among them was more important.
Therefore, there is no clear answer to the question.