The paper presents the experimental results on temperature dependences of electrical resistance of disordered single-walled carbon nanotube (SWNT) films on polyethylene terephthalate (PET) substrates and discusses the piezoresistive effect studied in the films within the strain ranging from –0.15% to +0.15%. The nanotubes were prepared by catalytic disproportionation of carbon monoxide on Fe particles obtained by ferrocene vapor decomposition. SWNT films were prepared by their in situ deposition on silicon substrates and transferred to PET substrates. Electron transport properties were studied from room temperature down to 77.4 K. It is shown that the experimental data are described by the fluctuation-induced tunneling conduction model. The effective activation energy estimated by approximating experimental data varies from 175 meV to 6.5 meV for the samples with the time of nanotube deposition varying from 5 min to 120 min, respectively. The strain gauge factor measured in the film with the smallest sheet electrical resistance appeared to be negative and equal to –14.