Many writers have influenced The Spanish Tragedy, notably Seneca and those from the Medieval tradition. The play is ostensibly Senecan with its bloody tragedy, rhetoric of the horrible, the character of the Ghost and typical revenge themes.:27 The characters of the Ghost of Andrea and Revenge form a chorus similar to that of Tantalus and Fury in Seneca's Thyestes.:27 The Ghost describes his journey into the underworld and calls for punishment at the end of the play that has influences from Thyestes, Agamemnon and Phaedra.:33 The use of onomastic rhetoric is also Senecan, with characters playing upon their names, as Hieronimo does repeatedly. Hieronimo also references the Senecan plays, Agamemnon and Troades, in his monologue in Act 3, scene 13. The character of the Old Man, Senex, is seen as a direct reference to Seneca.
The play also subverts typically Senecan qualities such as the use of a ghost character. In Kyd the Ghost is part of the chorus, unlike in Thyestes where the Ghost leaves after the prologue. Also, the Ghost is not a functioning prologue as he does not give the audience information about the major action on stage nor its conclusion.:33 The Ghost is similar to those in metrical (meaning in meter form) medieval plays who return from the dead to talk about their downfall and offer commentary on the action. Revenge is akin to a medieval character that acts as a guide for those on a journey.