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On May 9, 2014, Disney XD announced that they renewed Lab Rats for a fourth season. There are 26 episodes this season. Filming started October 2014. The first episode was released on March 18, 2015. The premiere episode of this season was Bionic Rebellion. The finale episode of this season was The Vanishing.
- Bionic Rebellion (403/404) - March 18, 2015
- Left Behind (401) - March 25, 2015
- Under Siege (402) - April 1, 2015
- Bionic Dog (412) - April 8, 2015
- Mission Mania (405) - April 15, 2015
- Simulation Manipulation (406) - April 22, 2015
- Forbidden Hero (408) - July 1, 2015
- Spider Island (409) - July 8, 2015
- Spike vs. Spikette (407) - July 15, 2015
- Lab Rats vs. Mighty Med (415) - July 22, 2015
- Space Elevator (414) - July 29, 2015
- Bionic Action Hero (410/411) - August 5, 2015
- One of Us (416) - August 12, 2015
- Bob Zombie (417) - September 30, 2015
- Human Eddy (419) - October 14, 2015
- The Curse of the Screaming Skull (420) - October 21, 2015
- Lab Rats: On The Edge (421/422) - November 11, 2015
- Ultimate Tailgate Challenge (413) - December 2, 2015
- And Then There Were Four (418) - January 13, 2016
- Space Colony (423/424) - January 20, 2016
- The Vanishing (425/426) - February 3, 2016
- Billy Unger as Chase Davenport/Spike (26/26)
- Spencer Boldman as Adam Davenport (26/26)
- Kelli Berglund as Bree Davenport/Spikerella (26/26)
- Tyrel Jackson Williams as Leo Dooley (26/26)
- Hal Sparks as Donald Davenport (15/26)
- Jeremy Kent Jackson as Douglas Davenport (15/26)
- Maile Flanagan as Terry Perry (11/26)
- Brandon Salgado-Telis as Bob (11/26)
- Angel Parker as Tasha Davenport (5/26)
- Max Charles as Spin (4/26)
- Jessalyn Wanlim as Giselle Vickers (4/26)
- Ashley Argota as Taylor/Taylor (3/26)
- Pearce Joza as Daniel Davenport (3/26)
- Graham Shiels as Victor Krane (2/26)
- Cole Ewing as Sebastian (2/26)
- John Eric Bentley as Mr. President (2/26)
- Mateus Ward as Marcus Davenport (2/26)
- Grace Kaufman as Kerry Perry (1/26)
- Michaela Carrozzo as Caitlin (1/26)
- Will Forte as Eddy/Human Eddy (1/26)
- Marissa Cuevas as Lexi
- Joel Michael Kramer as Tank
- Jumpy the Dog as Otis
- Judith Drake as Mrs. Stern
- Liana Ramirez as Kate/Spikette
- Mar Mar as Reggie
- Ryan J. Kelly as Thermo Hands
- Damion Poitier as The Incapacitator
- Mark Saul as Dr. Ryan
- Leo Howard as Troy West
- Emery Kelly as Logan
- Ping Wu as Dr. Gao
Special Guest Cast
- Bradley Steven Perry as Kaz
- Jake Short as Oliver
- Paris Berelc as Skylar Storm
- Carlos Lacámara as Horace Diaz
- Jilon VanOver as Tecton
- Jenelle McKee as Gamma Girl
- Esteban Cueto as Gray Granite
- Willie McGinest as Himself
- This is the only season that premiered in March.
- This season is renamed to Lab Rats: Bionic Island. It also features an updated beginning to the intro.
- This season makes Lab Rats the 2nd Disney XD series to make it to Season 4.
- There were five one-hour episodes (not including the crossover): Bionic Rebellion, Bionic Action Hero, Lab Rats: On The Edge, Space Colony, and The Vanishing. This is the most one hour episodes in a season.
- Spike returned in Spike vs. Spikette, along with another student with the Commando App (Spikette) and Bree's Commando App, (Spikerella).
- Leo was given a bionic leg to replace his injured one in Space Elevator.
- This Season introduces a new Big Bad, Giselle Vickers.
- There was a crossover this season with Mighty Med in Lab Rats vs. Mighty Med.
- This season features two new sets, the Mentor Quarters and the Davenport Bionic Academy.
- Hal Sparks directed the episodes Left Behind, Spider Island, and Space Elevator.
- Marcus Davenport, Taylor and Victor Krane all return this season after the latter two were presumed deceased, while the former was brought back to life after being destroyed. Out of the three, Taylor is the only one still alive, and the only one to join the good side.
- A new bionic sibling is introduced this season, Daniel Davenport.
- The season and series finale, The Vanishing, aired February 3, 2016.
- This is the only season that Rose, Janelle and Trent don't appear.
- Donald was absent in eleven episodes. (Under Siege, Bionic Dog, Mission Mania, Forbidden Hero, Spider Island, Spike vs. Spikette, Bionic Action Hero Part 1 & 2, One of Us, Bob Zombie, The Curse of the Screaming Skull)
- This is the only season to have a 1-hour finale.
- Even though it shows Chase using his original forcefield he never uses it this season.
- This season Adam is 19–20, Bree is 18–19, and Chase and Leo are 17–18.
- However, this is contradicted in Elite Force, when Bree is stated to be 17 during Sheep-Shifting.