All of Rick Riordan's book are set in the same universe, meaning that they all interact with each other and all interact with each other anyway from meeting in person to mentioning each other.
The series makes occasional references to the Camp Half-Blood series, as it takes place in the same world.
- Amos Kane states that Manhattan has its own set of gods and that they must be kept separate from Egyptian gods. He says this while looking at the Empire State Building, the current home of Mount Olympus.
- Thoth makes a vague reference to the Percy Jackson and the Olympians series when he mentions Hermes, who he states is nothing like him. This hints that he has seen Hermes and that the Greek and Egyptian gods might interact. This statement, however, might not be reasonable if he is inside a host, since the host isn't him. If this is the case, he might be comparing their true forms. He may not have a host, which would be more reasonable as he should he able to inhabit a place of learning in his true form like Anubis can in a place of death.
- Anubis seems to have the same appearance as Nico di Angelo from the Camp Half-Blood Series. Also they have the same nickname, "Death Boy".
- In the epilogue of the graphic novel, Sadie is seen wearing a Camp Half-Blood T-shirt and Carter is seen wearing an outfit nearly identical to what Percy Jackson wore on the cover of The Lightning Thief.
- Carter catches a glimpse of a winged horse flying around Manhattan, and recalls what Amos said about Manhattan and its gods. In The Son of Sobek, Carter believes that the winged horse is a Pegasi.
- Carter makes another allusion to Percy Jackson, when he's drowning and wishing he had sea god powers.
- The Roman ghosts that appeared later in the story mentioned the Roman gods Jupiter, Pluto, and Vulcan. Later, when they were destroyed by Ptah, he mentioned they went on to whatever afterlife awaits them, referring to the Underworld.
- At the end of the graphic novel, Carter is seen wearing a Camp Jupiter T-shirt.
- Lacy and Drew from Camp Half-Blood make an appearance at a school dance that Sadie attends. In fact, Lacy even mentions that they go to a summer camp together and Drew is a tyrant there as well as at school.
- Sadie's mom claims there will be other gods and rival magic that Sadie and Carter will encounter in the future, since the Egyptian gods have temporarily retreated from the mortal world.
- Walt explains to Sadie that in the world of the gods (i.e., both the Camp Half-Blood series and The Kane Chronicles) that a person who dies and goes to the Underworld, they go to the one they believe in. I.e, if a believer is mummified, yet believes in the Greco-Roman Underworld, they will go to Hades'/Pluto's Underworld.
- At the end of the book, Sadie says that they're picking up unidentified magical energy coming from Long Island. Camp Half-Blood is in Long Island.
The Son of Sobek is a short story featuring both Percy Jackson and Carter Kane, with the audiobook narrated by Rick Riordan himself. In it, Percy Jackson and Carter Kane combine forces to defeat a common enemy. See The Son of Sobek for a full summary.
The Staff of Serapis is another short story featuring Sadie Kane and Annabeth Chase. Annabeth and Sadie combine forces to defeat Serapis, the Greco-Egyptian god. See The Staff of Serapis for a full summary.
- Apollo mentions Ra riding his sun boat across the sky.
- Annabeth mentions her cousin and uncle in Boston who are Magnus Chase, Norse Demigod Son of Frey, and Randolph Chase.
- Magnus Chase is the cousin of Annabeth Chase.
- Magnus wants his sword to turn into a pen (and jokes about how absurd it is), making reference to Riptide.
- Annabeth appears in the beginning of the book, searching for Magnus, with her father, Frederick Chase.
- Annabeth tries to convince Magnus to come to a place where he will be safe. She is talking about Camp Half-Blood or Camp Jupiter.
- One of the chapter titles contain Jason Grace's name, though it says immediately after that Magnus has no idea who Jason is.
- At the end of the book, Magnus and Annabeth meet up, and presumably tell each other about the different gods.
- Magnus, since meeting up with his cousin, is now aware of the Greek Gods in New York City.
- Annabeth tells Magnus about 'a fallen god', Apollo. As well as the trouble they are having with immortal Roman emperors.
- When Apollo goes to Percy's apartment, Percy mentions that Annabeth is in Boston for a family emergency.
- Apollo mentions Sol, the Norse sun god, running from wolves across the sky.
- Apollo mentions coming across a "hot God" in Stockholm and it references this god having a "Talking sword that won't shut up". This god is Frey.
- The timeline of the crossovers take place after The Blood of Olympus.