Alkynes and phenoldiazoniumsalts undergo a Pd‐catalyzed [2+2+1] cyclization reaction to spiro[4,5]decatetraene‐7‐ones. This structure was confirmed for one example by X‐ray single‐crystal structure analysis. The reaction is believed to proceed through oxidative addition of the phenoldiazonium cation to Pd0, subsequent insertion of two alkynes, followed by irreversible spirocyclization.