Lukasz Furmanek, aged 24, was killed and Radoslaw Dudek left clinging to life following the attack in May.
Abdullah Atiqzoy, aged 18, from Oldbury and Sadam Khan Essakhil, 16, from Small Heath, Birmingham, were each found guilty of murder and attempted murder at Birmingham Crown Court today.
Sentencing was adjourned, but both were told they would be given life sentences.
Feizullah Atiqzoy, aged 24, from Swan Crescent, Oldbury, was also found guilty of assisting an offender.
The two men were stabbed in Grove Lane, Handsworth, after being approached by the teenagers.
Abdullah Atiqzoy, from Elizabeth Crescent, and Essakhil, who can be named after reporting restrictions were lifted, had denied the charges but were found guilty following a trial.
They were both also convicted of attempted murder.
Both remained emotionless as the verdicts were delivered yesterday, though Essakhil smiled towards his co-defendan afterwards in the dock. Atiqzoy sat with his face in his hands.
Judge Patrick Thomas QC told both they would be given life sentences.
During the trial, schoolboy Essakhil had admitted stabbing Mr Furmanek once but claimed he had acted in self-defence.
He also claimed the knife was Mr Furmanek's and he had picked it up after the victim dropped it.
However, the prosecution claimed the two teenagers had attacked the two Polish men in a 'chilling' act of violence and that the pair were 'excited' about being armed with knives and ready to confront the first men they came across.
The Crown said the acts were a 'joint enterprise' and both had intended to kill.
They will be sentenced on january 15.