- "That won't help my investment portfolio!"
- Robert gets angry after the investment company he was using went down.
Robert Jefferson is the father of Rowley Jefferson, the husband of Mrs. Jefferson, the brother of Rowley's Uncle and son of Rowley's Grandfather. He appears as a minor antagonist. He is one of the wealthiest people in Surrey Street, as well as the least respected in his neighborhood. In the movie, he is played by Alf Humphreys. He has an on-and-off hatred towards Greg because he sometimes believes he was a bad influence on Rowley.
He is an extremely overprotective but well-intentioned parent and won't let Rowley play any video games with the slightest bit of violence or fighting in it, as he sees them as things that could change Rowley into a different person. In Old School, he is seen yelling at Rowley to put a stick down. He won't even let Rowley use the internet. He does not like criticism from people he dislikes, as seen in Dog Days. In the events of Dog Days, it is shown that he can simply restrict people he dislikes from ever entering his country club again if they dare give any type of criticism about him or any of his property. He thinks that Greg is a bad influence on Rowley, and he, in Dog Days, also banned Rowley from seeing Greg for a whole Summer. Even though he keeps telling Rowley to stay away from Greg, his wife however thinks it is a good idea for having Greg to accompany Rowley and he even once hired a Cool Brian for Rowley when he broke up with Greg. He also seems to do investment portfolios as shown in The Third Wheel for a company with Dow Jones Industrial Index.
Greg depicts Mr. Robert Jefferson with afro style hair, black shirt, and long pants. In ''Dog Days'', it is shown that he wears pajamas when he is sleeping. He returned in the film version of ''Rodrick Rules'' but has no dialogue. He only appears to pick up Rowley after Rowley had sat on the tin-foil ball covered with toothpicks that Manny made for Greg as a apology gift and after Rowley freaked out from watching the movie The Foot and Greg was forced to apologize to Robert for choosing an "inappropriate" movie.
Appearance in Poptropica
He is shown to have white hair as seen in the movie, but in Wimpy Kid Boardwalk island in Poptropica had shown he has blonde hair, just like his son Rowley and his wife Linda. He wears a lavender shirt,black shorts, and brown shoes.
- His first name is revealed in Dog Days when Susan Heffley replies to his email account, thinking he sent the SOS email when Greg actually sent it.
- He did not appear in Diary of a Wimpy Kid: Double Down, same as Linda Jefferson.
- It has been shown that he sometimes dislikes Greg mainly because he sees Greg as a bad influence for Rowley as seen in Diary of a Wimpy Kid: The Ugly Truth also because Rowley almost always gets injured in almost every sleepover as seen in the Rodrick Rules.
- In the book The Third Wheel it is revealed that he is a stock market investor which would explains their family's wealth.
- Greg uses Mr. Jefferson as a chauffeur on his date with Abigail Brown in order to impress her. Mr Jefferson is somewhat offended when Greg refers to him as "driver".
- Diary of a Wimpy Kid Online (First appearance)
- Diary of a Wimpy Kid (First book appearance)
- Diary of a Wimpy Kid (film)
- Diary of a Wimpy Kid: Rodrick Rules
- Diary of a Wimpy Kid: Rodrick Rules (film)
- Diary of a Wimpy Kid: The Last Straw
- Diary of a Wimpy Kid: Dog Days
- Diary of a Wimpy Kid: Dog Days (film)
- Diary of a Wimpy Kid: The Ugly Truth
- Diary of a Wimpy Kid: Cabin Fever
- Diary of a Wimpy Kid Do-It-Yourself Book
- Diary of a Wimpy Kid: The Third Wheel
- The Wimpy Kid Movie Diary (Appears in all 3)
- Diary of a Wimpy Kid: Old School
- Diary of a Wimpy Kid: The Getaway
- Diary of a Wimpy Kid: The Meltdown
- Diary of an Awesome Friendly Kid: Rowley Jefferson's Journal