Kello, 30, has spent the week training at the club's Compton facility as manager Dean Saunders ran his eye over the stopper, who is a free agent.
Relegation-threatened Wolves have been on the lookout for reinforcements with first-choice Carl Ikeme facing the remainder of the season on the sidelines having broken his hand punching a dressing room tactics board at the interval against Bristol City last time out.
With Wayne Hennessey (knee) already sidelined, Dorus De Vries is set to take the number one shirt for Saturday's home clash against Middlesbrough, while Aaron McCarey has already been recalled from his loan spell at Walsall as back-up.
Saunders told the club's official website: "Obviously having lost Carl we needed some cover in case Dorus gets injured and have recalled Aaron from Walsall.
"Marian is an experienced goalkeeper and a Slovakian international and if he has to step in he will be able to deal with it.
"Aaron will probably be on the bench on Saturday but we need the extra cover for the final eight games of the season."
Kello spent four successful years with Hearts between 2008 and 2012. He departed the Scottish club in April 2012 amid heavy interest from several top-flight suitors including Aston Villa, before he undertook trial periods with Ipswich and then Wolves last summer when former boss Stale Solbakken was in charge.