Inclusion Criteria:

* Have a diagnosis of IPF within the previous 5 years from time of screening and confirmed at baseline
* FVC >/=40 percent (%) and </=100% of predicted at screening
* Stable baseline lung function as evidenced by a difference of less than (<) 10% in FVC (in liters) measurements between screening and Day 1, Visit 2 prior to randomization
* DLco >/=25% and </=90% of predicted at screening
* Ability to walk >/=100 meters unassisted in 6 minutes
* Cohort A: No background IPF therapy for >/=4 weeks allowed prior to randomization and throughout the placebo-controlled study period
* Cohort B: Tolerated dose of pirfenidone </=2403 milligrams once daily (mg/day) for >/=4 weeks required prior to randomization and throughout the placebo-controlled study period

Exclusion Criteria:

* History of severe allergic reaction or anaphylactic reaction to a biologic agent or known hypersensitivity to any component of the lebrikizumab injection
* Evidence of other known causes of interstitial lung disease
* Lung transplant expected within 12 months of screening
* Evidence of clinically significant lung disease other than IPF
* Post-bronchodilator forced expiratory volume in 1 second (FEV1)/FVC ratio <0.7 at screening
* Positive bronchodilator response, evidenced by an increase of >/=12% predicted and 200 milliliters increase in FEV1 or FVC
* Class IV New York Heart Association chronic heart failure or historical evidence of left ventricular ejection fraction <35%
* Hospitalization due to an exacerbation of IPF within 4 weeks prior to or during screening
* Known current malignancy or current evaluation for potential malignancy
* Listeria monocytogenes infection or active parasitic infection within 6 months prior to Day 1, Visit 2
* Active tuberculosis requiring treatment within 12 months of screening
* Known immunodeficiency, including but not limited to human immunodeficiency virus infection
* Past use of any anti-interleukin (IL)-13 or anti-IL-4/IL-13 therapy, including lebrikizumab
* Evidence of acute or chronic hepatitis or known liver cirrhosis

Exclusions Criteria Limited to Cohort B:

* Known achalasia, esophageal stricture, or esophageal dysfunction sufficient to limit the ability to swallow oral medication
* Tobacco smoking or use of tobacco-related products within 3 months of screening or unwillingness to avoid smoking throughout the study period
* Known or suspected peptic ulcer
* Any condition that, as assessed by the investigator, might be significantly exacerbated by the known side effects associated with pirfenidone
* Creatinine clearance <40 milliliters/minute, calculated using the Cockcroft-Gault formula
* Use of following therapies within 4 weeks of randomization (Day 1, Visit 2) or during the study: Strong inhibitors of CYP1A2 (Cytochrome P450 Family 1 Subfamily A Member 2) (example: fluvoxamine or enoxacin); Moderate inducers of CYP1A2 (limited to tobacco smoking and tobacco-related products)