The league's two top teams will meet in the Eastern Conference finals while the Portland Timbers learned their opponents in the West.
Atlanta put together a 3-1 win on the day and a 4-1 aggregate victory over NYCFC, booking a date in the Eastern Conference final against the New York Red Bulls.
The Paraguayan star's set piece highlight came moments before halftime, as Almiron curled a shot past the wall and a diving Sean Johnson to give Atlanta a 2-0 lead on the day and a 3-0 advantage on aggregate.
— Major League Soccer (@MLS) November 11, 2018
Martinez opened the scoring for Atlanta, converting from the penalty spot after Ismael Tajouri-Shradi took down Franco Escobar in the penalty area.
The Venezuelan star's goal came 17 minutes before Almrion's incredible free kick, giving Atlanta a three-goal cushion.
The home side nearly needed it as NYCFC found a lifeline just before the halftime break with Maxime Chanot scoring in stoppage time to keep hopes alive.
Martinez put that idea to bed, though, scoring in the 83rd minute to seal Atlanta's spot in the next round.
The Five Stripes will face the New York Red Bulls once they get there after the Supporter's Shield winners came from behind to edge the Columbus Crew following a 1-0 first leg loss.
Playing at home, the Red Bulls thumped the Crew 3-0 to book their own conference final spot behind a Daniel Royer brace.
The Austrian winger scored goals just three minutes apart, giving the Red Bulls the lead before adding a major cushion moments later.
— Major League Soccer (@MLS) November 12, 2018
His first came in the 73rd minute as Royer capped an incredible passing sequence with a finish from near the penalty spot. His second came moments later with Royer cutting in and firing a shot that slipped past Zack Steffen.
Alex Muyl opened the scoring while leveling the aggregate series, deflecting home an Aaron Long shot in the 17th minute to set a tone that continued on through Royer's goals.
In the West, the conference final matchup is set as Sporting Kansas City joined the Timbers thanks to a win on Sunday.
Sporting KC edged Real Salt Lake 4-2 on the day and 5-2 on aggregate by holding off a second-half comeback at Children's Mercy Park.
Up 2-0 on the day through Diego Rubio and Daniel Salloi goals in the 14th and 19th minutes, SKC let RSL back into the match in the 60th minute on a Sebastian Saucedo goal.
Ilie Sanchez scored for SKC seven minutes later to restore the two-goal lead before Damir Kreilach brought RSL back within one in the 72nd.
However, a 97th minute finish from Salloi ended the match while sealing SKC's spot in the conference finals.
With the two matchups now set, the Red Bulls will visit Atlanta and the Timbers will host Sporting KC on November 25 before return legs four days later.